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Saluting our volunteers

John Latham

6 January 2023

The Trust is very fortunate to count on the support of a group of dedicated local volunteers who offer their time on Saturday mornings several times each year.

Under the guidance of Trustee Max Field, the most recent work party gathered on 29th October to clear debris and fallen branches in the section from Bentley Road to the Brick Bridge, and to plant bulbs in the woodland along the Conduit. Coffee and biscuits kindly provided by Vicky Field provided a welcome celebration of the morning’s achievements.

We have also been delighted to benefit from the regular efforts of volunteer working parties from Mace Limited who work on the Biomedical Campus, and focus on clearing the section of the Brook that runs by Clay Farm.

On 26th September a dozen volunteers from AstraZeneca spent the day on a variety of tasks, clearing vegetation from the path and debris from the Conduit, planting bulbs and waterside plants, and cleaning graffiti from the Memorial Bridge. They varnished and repainted the placard, and applied oil to the parapets. The day was co-ordinated by Employee Volunteering. This enthusiastic group included members of AstraZeneca staff from Cambridge, London and Berkshire, and we look forward to their next day with us.

The Trustees are grateful for the support that we receive from the City Council and the City’s local nature reserve volunteers.

All the efforts made by volunteers tend to be unseen other than by passers-by at the time, but the results of these endeavours are appreciated throughout the year.

The Trustees enjoy opportunities to participate with the volunteers in work on the Brook and Conduit, but we mainly want to salute the work of our volunteers and express our sincere thanks to them.

De-silting the Conduit

John Latham

22 December 2022

Update to news article dated 27 January 2022 below.

In February 2022, using a 1.8 tonne Hitachi excavator, a Youngman moveable bridge and wheelbarrows, an experienced team from our contractors, SP Landscapes, excavated a channel through the silt between the Memorial and the Accordia Bridges.

The silt was placed mainly onto the eastern bank of the Conduit.

There has been a lasting improvement in flow along the Conduit and there is evidence that the higher flow has produced natural scouring of the bed in that section, and to a lesser extent downstream. Better flows encourage fish and wildlife.

Using a similar technique we anticipate that we will begin de-silting the section north (downstream) of the Accordia Bridge in March 2023.

MKA Ecology have carried out a repeat of their preliminary water vole survey, and a further survey will take place before work commences. We continue to be advised by Cambridge City Council.

At this juncture it is too early to give more specific details on timing, but notices will be posted.

It is likely that, given the narrowness of the path by the Conduit between Brooklands Avenue and the Accordia Bridge, there will be three periods of several working days each during the proposed work when path users will be redirected along the Public Footpath to the west of the Empty Common Allotments.

We will also be carrying out bank repairs along the path. Notices will be displayed.

Tree work in preparation for major Conduit Head restoration

John Latham

16 December 2022

On Wednesday 8th December the yew tree next to the prominent Conduit Head Memorial by Lensfield Road was reduced in accordance with the permission received from the City Council.

The Monument, opened to the public in mid-September for the first time as part of Open Cambridge this year, was the public water fountain that stood in Cambridge Market Place from the early 1600s.  When he died in 1631, Thomas Hobson left land charged for the upkeep of the watercourse and funds for improvement of the working of the Conduit, which we take to mean the fountain and its operation.

The yew tree, which was probably planted in the mid 20th Century had grown to the point where it was brushing against the Listed and Scheduled Monument, contributing to the wear and tear of the Monument.

This tree work is a precursor to the major restoration of the Monument and the listed railings from the mid 19th Century that surround it.

The Trust has sought the necessary permissions, and with help and advice from local specialists Brown & Ralph and Navigate Planning in Ely, we are now proceeding towards settling the programme for a major restoration project.  This will be the first work on the Monument for over fifty years, and will probably be the first time that the railings have been fully restored since their installation in 1856.  It is likely that some railings will need to be removed to workshops for restoration.

Paint analysis has been conducted, and we will aim to bring the railings back to their original colour.

More details of our plans will be published here.

Hobson’s Brook Bioblitz 2022 Brief Report – More than 200 Species Identified

Dr Steve Boreham – Bioblitz Science Co-ordinator 

Hobson’s Brook Bioblitz took place on the 10th and 11th June 2022.

The Bioblitz was held at Clare Wood and the North Meadow, adjacent to Clare College Playing Field, Bentley Road, Cambridge. Both Clare Wood and the North Meadow occupy a position between Hobson’s Brook and Vicar’s Brook. More than a dozen experts and volunteers ran hour-long identification sessions and guided walks at the site. Over a hundred people participated in the event, enjoying the sunny weather. The Bioblitz sessions covered plants, small mammals, birds, bats, moths, other insects and freshwater invertebrates.

Clare Wood and the North Meadow produced 211 different taxa (mostly identified to species level). These included 26 species of birds, 12 mammals, 3 fish, 1 amphibian, 95 types of invertebrates (including 59 moths) and 74 different plant species.

These results compare well with the 2019 Bioblitz at Clare College Playing Field and highlight the diversity of habitat present along this part of the Hobson’s Brook corridor.

Bioblitz highlights were the Blackcap, Kingfisher, Buzzard and Little Egret, the Brown Oak Tortrix Moth and Grass Rivulet Moth, the Serotine and Noctule Bats, the Bank Vole and Otter, the Broad-bodied Chaser Dragonfly, and the Common Spotted-orchid.

This Bioblitz has emphasised the biodiversity of green spaces close to the built environment, and shows the importance of the Hobson’s Brook ‘green corridor’ in preserving wildlife in the City of Cambridge. Maintaining a strong flow of high quality water in Hobson’s Brook is clearly essential for the continued success of these ecosystems, which offer considerable benefits to the people that live close by.


Bioblitz returns for 2022

Author: John Latham

16 May 2022

FRIDAY 10TH JUNE 5pm – 11pm

SATURDAY 11TH JUNE 8am – 1pm

Clare College Sports Ground Bentley Road, Cambridge


Back for 2022! Bioblitz is our annual public-participation survey of the wildlife present along the Hobsons Brook corridor.

Includes small mammal identification, bat detection, moth trapping, bird spotting, butterfly identification, plant identification, examining freshwater invertebrates, guided walks along Hobson’s Brook.

Ideal for families

Family activities for novices, enthusiasts and experts – young and old (under-16s to be accompanied)

All events free of charge

Register on the day

Download and print the flyer here

Find us

By kind permission of the Master and Fellows of Clare College, all activities begin at Clare College sports ground, which can be reached via Bentley Road or on foot via the footpath along the brook.

Use the map on the left or click here: ///

2019 Results

Our June 2019 Bioblitz was also based at Clare College Sports Ground, and concentrated on the adjacent areas of woodland, close to meadows between Hobson’s Brook and Vicar’s Brook.

A dozen experts and volunteers ran hour-long identification sessions and guided walks at the site. The event was well attended, despite the wet weather. The Bioblitz sessions covered plants, small mammals, birds, bats, moths, and other insects and freshwater invertebrates.

Clare College Sports Ground produced 205 different taxa, including:-

  • 36 species of birds
  • 8 mammals
  • 71 types of invertebrates (including 48 different moths) and 89 different plant species.

Bioblitz highlights were the Tawny Owl, Kingfisher, Sparrowhawk and Little Egret, the Poplar Hawk- Moth and Spectacle Moth, the Serotine and Soprano Pipistrelle Bats, the Wood Mouse and Bank Vole, the Water Scorpion, and the Grey Poplar, Lesser Water Parsnip and Stinking Iris.

These results compare well with the 2018 Bioblitz at Hobson’s Park, Trumpington, and the 2017 Bioblitz at Nine Wells and Empty Common, and together emphasise the diversity of habitat present along the Hobson’s Brook corridor.

2022 programme

This year we will focus on the North Paddock and the adjoining woodland between Hobson’s Brook and Conduit and Vicar’s Brook. This is the programme:-

Friday evening 10th June
Trustee Guided Walks 5.15pm onwards
Bird spotting 6 – 7pm
Small Mammals 7 – 8pm
Bat Detection 9 – 10.30pm
Moth trapping 10.30 – 11pm


Saturday morning 11th June
Small Mammals 8-9am – 1pm
Moth trapping 9 – 10am
Bird spotting 9.30 – 10.30am
Butterflies 10 – 11am
Plant identification 11am – 12 noon
Freshwater invertebrates 12 noon – 1pm


On Friday early evening and on Saturday morning Trustees will conduct guided walks along Hobson’s Brook and Conduit.

Our programme of Bioblitz events has highlighted the biodiversity of green spaces close to the built environment, and shows the importance of the Hobson’s Brook ‘green corridor’ in preserving wildlife in the City of Cambridge. Maintaining a strong flow of high quality water in Hobson’s Brook is clearly essential for the continued success of these ecosystems, which offer considerable benefits to residents and visitors. The Hobson’s Brook corridor forms part of the Cambridge Nature Network.

De-silting the Conduit

Author: John Latham

27 January 2022

Area of desilting operations 2022

For some time the Trustees and those who take a close interest in Hobson’s Brook and Conduit have been concerned about the volume of silt that has accumulated downstream from the Memorial Bridge where the main spillway to Vicar’s Brook takes off a large portion of the flow from Hobson’s Brook.

Achieving a reduction in the volume of silt is particularly challenging because access to the Conduit is very constrained. Removal of a portion of the silt was achieved in 2020 along the Botanic Garden bank. The silt extracted was used to backfill the trench created to take the steel piling inserted along much of the bank to stop the leaks from the Conduit through the bank into the Garden.

Further upstream we have only the relatively narrow margins of the Conduit available to take the silt, and otherwise we would need to transport the silt off site. This is made more difficult because we need to remove water from the silt before it can be taken away, and despite a sustained effort to find an acceptable approach to de-watering, this remains elusive. We continue to investigate how this could be achieved without the use of potentially noxious chemical flocculants. Limited space precludes natural drying of the volumes of silt envisaged.

The Trustees have also been concerned not to cause any unnecessary disruption to the ecosystem. The dimensions of the Conduit mean that the smallest amphibious machinery available would only just fit within the Conduit’s margins.

Recent work on bank repairs by the Memorial Bridge has shown that a small 1.8 tonne Hitachi excavator can operate from the path, and with the use of wheelbarrows and a moveable temporary ‘bridge’ it is possible to remove a worthwhile volume of silt and place some of it onto the eastern bank. Some silt was used to complete bank repairs and these areas will soon be planted with carefully chosen native species.

We have therefore decided to continue with this experimental silt removal method, and in February we aim to excavate a channel some 50 cms wide and 40 cms deep between the Memorial Bridge and the Accordia Bridge.

The objective will be to improve flow, and encourage the higher flows that are experienced in spring and early summer to scour more silt. The initial experimental silt removal has already started the scouring process downstream from the Memorial Bridge. We have reopened the penstock close to the Conduit Head which takes water from the Conduit down Fen Causeway to Coe Fen. This has improved the flow along the Botanic Garden and Brookside, and will enhance the water habitat on Coe Fen.

We have been advised by the City’s Biodiversity Officer, and we will cease work in time for the bird nesting season.

If February’s experiment is successful, we intend to resume silt removal using a similar method in late autumn and winter 2022-23 with the object of achieving a similar impact in the section between the Accordia Bridge and Brooklands Avenue. Because the path along this section is relatively narrow, a path closure will be required, but the designated footpath around the Empty Common allotments will be available as the alternative route.

One of the consequences of the build-up of silt is that the bed of the Conduit has been raised, and the water level is therefore higher, which contributes to leaks. Other consequences are the shallow depth of water and slow, sometimes imperceptible flow. This is not conducive to a good, rich and diverse habitat, but it is likely that some invertebrates benefit from shallow water.

We are therefore aiming to achieve a balance between different depths of water, and open up a main channel along the Conduit that will make the principal flow both deeper and faster.

The whole Conduit between Brooklands Avenue and the Memorial Bridge has been expertly surveyed for the presence of water voles by MKA Ecology Ltd. Currently the water voles appear to occupy several locations from the Memorial Bridge to just north of the Accordia Bridge. We are therefore using a de-silting approach that will minimise interference with the water voles’ habitat.

Cambridge City Council are supportive of this programme, and we are grateful for the enthusiastic interest and support that we have received from the Accordia residents, and the Empty Common allotment holders and community garden.

A further update will be posted in February once the current work is complete, and again later in the year once our programme for the sections of the Conduit downstream from the Accordia Bridge has been settled.

Repairs to the bench

Author: Max Field

9 December 2021

In October 2021, some of the wooden slats on the Hobson’s Brook bench between Brooklands Avenue and Accordia Bridge had been damaged.  By November further destruction meant that the bench had become unusable.

One of the Hobson’s Conduit Trust volunteers has repainted the metal sections of the bench and replaced the pine with new oak slats. The Trustees are particularly grateful to him for giving up time to undertake this project on our behalf.

A donation to the museum of Cambridge

Author: Max Field

2 February 2019


These bronze plaques were probably from on the Victorian fountain in Market Square. Mr Robert Noel from the College of Arms has identified them for the Trustees. The shields on the right are the Coat of Arms of Cambridge University (top) and Cambridge Town (bottom).

The others may represent benefactors. The plaque at the top left is the shield for the Fitzwilliam – Wentworth family. The red lozenges from the Fitzwilliam family and chevron with leopards from Watson Wentworth side. The two families were united in marriage in 1744.The other (bottom left) shield attribution is complex but may represent a variation of the Perne family crest.

The plaques were donated by the Trustees in 2017 to the Museum of Cambridge.