Brown’s Hotel on Albemarle Street claims to be the site of Britain’s (and London’s) first telephone call, made by Alexander Graham Bell in the 1870s.
 
In 1876/1877, during a visit from Boston, Alexander Graham Bell wanted to test his new telephone before pitching it to investors. He needed a private telegraph wire. The then owners of Brown’s, James John Ford and his son Henry, had exactly that: a private wire running about seven kilometres from the hotel to their family home in Ravenscourt Park.
 
Bell arrived at the hotel with a bag of equipment and made the call.
 
Interesting facts...
There are no records of the call but its a lovely story nonetheless