By Keily Oakes BBC News Online entertainment staff

Presenters Mark Radcliffe and Marc Riley, affectionately known as Mark and Lard, are going their separate ways when they leave BBC Radio 1 in the spring.

Mark Radcliffe and Marc Riley will leave Radio 1 in the spring

As well as saying goodbye to the duo, for some of their fans it could also be farewell to listening to Radio 1.

The station's target age group is 15-24 years but Mark and Lard's show stood out from the rest in appealing to older listeners.

"It seems their show has been something of an anomaly for the past few years in terms of their features and their level of sharp humour," Simon Garfield, author of The Nation's Favourite: The True Adventures of Radio 1, told BBC News Online.

"Their musical tastes are also at a variance with what they are obliged to play."

Conscious

He believes it makes "perfect sense" for Radcliffe to move to BBC Radio 2, while their successors Colin Murray and Edith Bowman could slip easily in to their slot because of their similar chemistry and double act routine.

There is a general opinion that bringing in younger presenters is a good move on the part of Radio 1, because it means a sharper focus on its core market.

"It is a wise move to bring in new faces especially as the BBC is very conscious of the charter renewal and sticking to its remit for the station and 'it's place in the world'," said Mr Garfield, whose book documented the mid-1990s upheaval at Radio 1 which saw Radcliffe and Riley come to prominence.

Comparing a schedule line-up from 1996 and the present day reveals just a handful of DJs have survived successive changes.

Simon Mayo and Nicky Campbell shifted to Radio Five Live, while Clive Warren and Mark Goodier moved on to commercial stations. Lisa I'Anson went to BBC London.

Simon Mayo is now on Five Live

Jo Whiley and Dave Pearce are still at Radio 1, having both worked their way up to prime daytime shows.

The only survivor of the "old guard" is John Peel, who continues to play his brand of experimental music, although he also has his BBC Radio 4 show, Home Truths.

"Whoever you talk to will have their own thoughts of the 'glory days' of Radio 1, probably from when they were 16 and the music and station meant something to them, such as going to a roadshow," said Mr Garfield.

"But the key for Radio 1 is to keep up with the times, which it seems to be doing."

'Vibe'

Michael Rosser, radio correspondent with industry magazine Broadcast, believes it was inevitable Radcliffe and Riley would be moved.

"Everybody has a lifespan on Radio 1 as it has to keep itself fresh, it has to keep a young vibe," he said.

"When you look at controller Andy Parfitt's strategy for the future it really was inevitable."

"Radio 1 is for the young of the country, if they are attracting an older audience that would not have been what Andy Parfitt was going for, and not what it is there for."

It could be argued the divide between Radio 1 and Radio 2 is often too great, leaving a gap for listeners aged over 25.

But Mr Rosser disagrees.

Colin Murray and Edith Bowman are expected to land daily slot

"I think there's enough to take listeners to Radio 2 with presenters such as Jonathan Ross and Mark Lamarr, who are entertaining broadcasters with encyclopaedic knowledges of music, who can also appeal to the more serious listener."

Mr Rosser thinks it is unfair on Radio 1 for critics to hark back to the days when it had audiences of 20 million - because then it had very little competition.

"Radio 1 still bringing in 10 million people is no mean feat, and it is still slick and is still sounding very fresh," he added.