In 1574 Andrew Perne, Master of Peterhouse and Vice-chancellor of Cambridge University that year, wrote to the Chancellor of the University, Lord Burleigh, about the recent outbreaks of the plague in Cambridge. In this letter he suggested taking water from the existing stream that flowed from Nine Wells in Great Shelford into the River Cam, and diverting it into Cambridge itself, in order to clean out the medieval King’s Ditch, on the southern and eastern edges of the town. The filthy state of the King’s Ditch was seen as being responsible for the plague.
By 1610 this “New River” had been constructed. In that year Thomas Chaplin, Lord of the Manor of Trumpington, signed a “tripartite agreement” with the town and the university giving them rights over the newly made watercourse and the soil either side in order to maintain it in good order. When Thomas Hobson, the well known Cambridge carrier (referred to in the phrase “Hobson’s choice”), died in 1631 he bequeathed land so that its income
could be used to maintain the supply of water to the market place, for in 1614 some of the water from the original stream had been diverted to Market Hill where it was used as a public water supply. Since that time the name of Hobson has been associated with the new stream and the water that it brings into Cambridge. It is not clear whether the stream ever achieved its original aim of flushing out the King’s Ditch, but the water has been put to a number of
alternative uses.
The original stream that fed the King’s Ditch ran down the centre of Trumpington Street, but is nowadays restricted to two “runnels” down either side of the road. They are fed by underground pipes which come from the Conduit Head at the junction of Lensfield Road and Trumpington Road. Since 1856 the Conduit Head has been graced by the presence of a structure (often, confusingly, also referred to as “The Conduit”) which originally stood in the market place, and provided the water supply which Hobson was so keen to
preserve. That had been fed by another underground pipe from the Conduit Head.
Two more underground channels leave the Conduit Head. One, now disused, ran under the old Addenbrooke’s Hospital (now the university’s Judge Business School) and the grounds of Pembroke College to feed the original University Botanic Garden north of Pembroke Street. The modern Botanic Garden alongside Trumpington Road also uses water from Hobson’s Conduit to fill its
lake.

The final underground watercourse started its life in about 1630 as an open channel, cut to deliver water to Emmanuel and Christ’s Colleges as well as to cleanse St Andrew’s Street. Ponds in the gardens of both colleges still benefit from a supply of “Hobson’s water”.
Since the early 17th century various benefactors, including Thomas Hobson, have given money and property for the benefit of maintaining Hobson’s Conduit. Those funds have always needed managing, and in the early years a group of feoffees were responsible for doing so, on behalf of both the town and the
university. In 1868 “The Conduit Trust” registered with the Charity Commission, and a revised scheme was approved in 1899, which is still in place today, with one recent amendment.
Under the 1899 scheme fifteen trustees were to carry out the business of the Trust. Five were “representative trustees” appointed by the Borough (now City) of Cambridge, and ten were “co-optative trustees” being “persons residing or carrying on business in or near Cambridge”. In recent years the City Council has ceased to appoint representatives to outside bodies, so the Trust has now obtained permission from the Council and the Charity Commission to convert the five representative positions into co-optative ones.
Today Hobson’s Conduit continues to benefit the people of Cambridge as a unique part of the city’s history, a green corridor that links the city centre and recent urban expansion with the countryside.

A fuller history was written by W D Bushell, and published by CUP in 1938: “Hobson’s Conduit: The New River at Cambridge commonly called Hobson’s River”.