Professor Stephen Hawking has shown his support for a local protest against plans to enlarge a hotel complex on the River Cam.

The physicist, 68, and many other local residents object to plans to build a three-story extension at the Hilton Doubletree Hotel than overlooks Mill Pond on the River Cam.

The Cambridge luminary attended a campaign picnic near the Hilton Hotel last Saturday, joining around 30 local residents.

Hawking and the residents argue the development would ruin a riverside area of natural beauty, once a favourite walking spot of Charles Darwin and other distinguished alumni.

Blue Badge tour guide Ruth Lambert, who organised Saturday’s action, said: “All the literati and scientists found it to be an extraordinary green finger into the centre of Cambridge and it’s anathema to have it covered in bling.”

But London-based hotelier The Ability Group, which proposes to develop the site, argues that extra rooms could be constructed “without detriment to the conservation area while also seeking to meet commercial aspirations and the wider economic needs of Cambridge as a flourishing regional centre”.

Cambridge MP Julian Huppert did not attend the picnic protest but added his support to the campaign, saying in a statement: “It would be a great shame to spoil the natural beauty of the area further”.

A petition against the proposed development has already gathered more than 100 signatures, including those of Hawkins and Huppert.

Residents have until this Friday to register their objections with Cambridgeshire County Council.

The Council threw out a similar application last year after objections from more than 160 residents, including Prof Hawking.