London (AFP) - Andy Murray warned Roger Federer to avoid sampling the questionable delights of a "horrific" deep-fried Mars bar after Federer accepted an invitation to play in Scotland for the first time.

World No. 1 Murray will face Federer in a charity exhibition match in Glasgow on November 7. Scotland is notorious for having one of the worst average diets in Europe, with the deep-fried Mars bar one of its most infamous dishes.

Murray and Federer may be rivals but that didn't stop the Scot from offering his Swiss counterpart some advice about the local 'cuisine'.

"Don't try the fried Mars bars," Murray joked. "I tried one of them for the first time last year and it was horrific. Stay away from them."

Federer won his 18th Grand Slam singles title at last month's Australian Open, beating old foe Rafael Nadal in a Melbourne final few pundits had foreseen.

"It's incredible what he did in Australia after such a long break," Murray said. "We play so much, a lot of the year. Sometimes coming to events fresh can have some huge advantage.

"Him and Rafa were both coming back from a pretty significant period of time out and they both played extremely well. Maybe that's something we can all learn from moving forwards."

Federer decided to take up Murray's invitation after the Scot took part in the Swiss ace's charity event in last April.

"I saw a little video where he was wearing a kilt when he was announcing that I was going to play in his event over in Switzerland," said Murray. "He's returning the favour in November. It's really good he's doing it.

"He's just extremely popular. He's one of the best players that's ever played the game. "It's not just how much he's won, but the way he plays and how he carries himself."

Federer will be helping raise funds that will be shared equally between the United Nations' Children's Fund (UNICEF) and an as yet unnamed local Scottish charity. "Last year was such a fantastic night and to raise over £300,000 (S$532,000) for UNICEF and Young People's Futures in our first year was amazing," said Murray, a UK ambassador for UNICEF.

"This year is going to be even bigger and better and I am so pleased to be able to bring Roger to play in Scotland for the first time."