Mark Skipper, aged 47, and his partner Neil Jarman, 43, were punched to the ground and repeatedly kicked as they returned to their hotel after watching a musical.
The couple were on a side street off Russell Square when they were attacked by four men in their early 20s.
Mr Skipper, chief executive of Northern Ballet Theatre, said: "This gang of lads came out of nowhere. I was whacked in the face and fell down and they were kicking and punching me and my partner.
"When I was half senseless they demanded money, so I gave them my wallet. They also took my mobile phone, a silver bracelet and my watch."
The pair, who were in London for the weekend, had planned to see another musical, but decided to return to their home in Cawthorne.
Mr Skipper said: "Because the company goes to Sadlers Wells and I am a big fan of the theatre I go to London all the time and we stay at the same hotel.
"It was a real shock. We both felt fortunate it was not more serious. You hear so much about gangs carrying knives these days, that we felt like it could have been much worse."