Ian McKellen leads London theatregoers in singing the 'Waiting for Godot' song he shared with late friend Patrick Stewart

Sir Ian McKellen, 87, made an unannounced appearance at the Denville Hall centenary fundraiser at Victoria Palace Theatre on Sunday, telling the audience he would speak without a microphone before leading performers and TV presenter Bradley Walsh in a rendition of 'Underneath the Arches'.

McKellen and Stewart had sung the same song nightly during their 2009 West End run of 'Waiting for Godot', reprising it on Broadway in 2013.

Stewart, who died on 28 October following battles with Alzheimer's disease and Lewy body dementia, had been McKellen's close friend for 50 years since they met at the Royal Shakespeare Company in 1974.

Oxford's St Catherine's College, where Stewart served as Cameron Mackintosh Visiting Professor from 2006, also paid tribute, calling him 'one of Britain's most distinguished actors'.