Television viewers serviced by a transmitter on Cane Hill Hospital grounds have been deprived of their favourite programmes several times since an arson attack damaged the electricity supply.

Since the attack on the Coulsdon hospital which drew in 43 fire engines and took six hours to extinguish on September 30 last year, the NTL transmitter has been powered by a generator instead of mainline electricity from the substation.

Bradmore Way resident Ian Scales, who is 74 and a retired engineer, claims he has by default become NTL's information service when transmission to his TV set fails, but the firm has now told him there could be trouble for the foreseeable future.

Mr Scales said: "Three times in the last 24 hours it's been off.

"They have told me just now that the generator needs to be fixed but the electricity people won't fix it until the security is improved over there.

"I don't watch the TV all the time but I'm retired so I am in a lot and do like to switch it on sometimes."

A spokesman for Crown Castle, which owns the transmitter, said they were negotiating with the landlord, NHS Estates Group, and electricity supplier, Seeboard, to restore a permanent power supply.

A spokesman for South London and Maudsley NHS Trust, which owns the Medium Secure Unit (MSU) at Cane Hill, said security presence on the site had dramatically increased recently in light of a spate of trespassing and vandalism in the last year.

He said the trust has submitted a business plan to take on full ownership of Cane Hill, which would make security easier to co-ordinate.

In the meantime the generator has been repaired and viewers can for the time being watch their televisions in peace.