A mystery voice is bugging radio listeners across Sussex - not least because guessing it correctly could win them £23,325.

The Southern FM name game, in which listeners have to name the mystery voice, is a hot topic of conversation.

It has been running for a record-breaking seven months and the prize is the biggest yet.

There is no limit to the size of the jackpot because every time someone guesses wrongly, it increases by £25. There have been 145,564 calls to the competition line so far.

Guesses so far have ranged from Enrique Iglesias and Zoe Ball to very obscure "celebrities". Others have included Ozzy Osbourne, Victoria Beckham and Tom Cruise.

So how have those in the know not succumbed to bribery, offers that cannot be repeated and gentle arm twistings by loved ones?

Only eight people are in on the secret and all have their lips tightly sealed.

Programme controller Tony Aldridge, who chose the mystery voice, said: "We cannot tell anyone the name, not even partners. It's in our contracts but at the end of the day it comes down to trust."

But that does not stop people trying to coax the name out of Tony and the others in the know - DJs Danny Pike, Nicky Keig-Shevlin, Richard Reynolds, Chris Copsey and Dan Gasser, one producer and former managing director Bob Hoad.

Mr Aldridge said: "People continually bug me about the name. I wouldn't tell my girlfriend or my mates. Lots of listeners email and say they will go halves with me.

"But I always tell everyone 'No, I'm not going to tell you'. I just want someone to guess the right name!"

The voice was chosen after Mr Aldridge sent a producer to find a celebrity voice saying a catchy phrase.

The snippet played of the mystery person saying "Who's that? Who's that?" is part of a longer recording which if played in full would identify them.

Anything from one to ten times a day, an alarm bell sounds and listeners have 30 minutes to call in with their guesses.

An independent company, Broadsystems, the same as is used by Who Wants To Be A Millionaire, selects a caller at random and faxes the name to the radio station.

The presenters have no way of knowing what name the callers are going to say until they go on air. This means the full recording is ready to play every time the game is played.

The recording is not locked in an underground vault but is on a computer hard disk.

Mr Aldridge, who admitted his big worry was the recording being played by accident, said: "At the beginning of the competition we got all the obvious guesses.

"Now the voice has really got into people's heads and everyone is dying to know who it is. Some people have said 'why don't you give subtle clues?' but we won't do that."

He said he hoped one lucky listener would hit the mark before Christmas. If not, the competition will be put on hold from December 20 to January 6.

The last Name Game jackpot, with actress Alicia Silverstone's voice, reached £16,075.