The singer and actor, 77, has been diagnosed with Meniere's disease and has cancelled a number of summer concerts on the advice of his doctors.

His agent Jennifer Maffini said: "There is an operation which could help, but it's not a guaranteed success and if things don't work out it could leave him deaf.

"He has seen various specialists and had all sorts of tests.

"It just creates a feeling of dizziness. It's not that it affects his singing, but it means it's impossible for him to travel to the venues."

The British crooner is a veteran of 19 Royal Variety Shows and is famous for songs such as You Need Hands and Tulips from Amsterdam.