Step outside the front door of Celtic Park and London Road lies about 150 metres at the bottom of Kerrydale Street.

Turn left and if you want you can keep on the same road, hit the M74 and head south until you cross the Scottish border and to eventually reach The Smoke if your heart desires.

The main artery between Scotland and England has been a much-travelled route over the years for Celtic players for whom the grass has indeed looked greener on the other side of Gretna.

Over the years, the likes of Davie Hay, Kenny Dalglish, Pat Crerand, and before them Bobby Collins, have been lured south by the prospect of a new challenge – and bigger paypokes.

And that is the price Celtic have always paid for rearing teams weaned on success.

Fast forward to the present day and the age-old concern of the club losing its best players to predatory cross-border raiders remains as potent as ever.

Neil Lennon's side are on course for a domestic treble.

And their awe-inspiring run to the last 16 of the Champions League, which included taking the prized scalp of Barcelona in the group stage, raised the stock of his team even higher.

All of which inevitably guaranteed the presence of suitors armed with big cheques the minute the January transfer window creaked open.

Top scorer Gary Hooper has attracted interest from the likes of Norwich and Southampton and has so far failed to put pen to paper on a new extension to his deal which concludes at the end of the current campaign.

Victor Wanyama is also stalling on fresh contract, a delay that has alerted Arsenal and Man United, with speculation suggesting a £10million bid could be on the way for the powerful Kenyan midfielder.

Then there is Fraser Forster, the ole goalie whose saves helped propel Celtic into their last-16 glamour tie with Juventus and earned him a place in Roy Hodgson's England squad.

Covetous eyes are on them all. It's a scenario that is all too familiar to Bertie Auld, the Lisbon Lion who himself left the club to sample football in England before making the return journey to cement his place in Celtic folkore.

But while Auld admits that a glance at the history books will underline that Celtic have always been a selling club the Sixties star admits that such is the quality of the present Parkhead ensemble that the prospect of a talent drain down south is particularly worrying this January.

Auld said: "If you go all the way back to the 1950s Celtic have always been a selling club. Back then Bobby Collins was the man and he went to Leeds United and then in the Sixties Paddy Crerand went on to Manchester United in 1963 and I went to Birmingham in '61 before coming back to Parkhead.

"Then you can trace your way through the Seventies with Davie Hay going to Chelsea and Kenny Dalglish to Liverpool and in the Eighties Charlie Nicholas went to Arsenal. But when these guys left it was one player here or there.

"The thing is the current side has so many good players that they could end up losing three or four in this window and that would be a massive problem. There has been plenty of talk about Hooper and Wanyama as they are out of contract at the end of the season and have failed to sign any extensions.

"But from where I am sitting this current Celtic side has players in every position that would cut the mustard down south. Look at Georgios Samaras – in Europe he has been immense.

"Beram Kayal in midfield has a lot of class and Adam Matthews has just got better and better. So I think there is real concern that we could lose more than one player during the January window.

"We all know the advantage that the English clubs have in terms of the cash they can splash due to their TV revenues and the attraction of playing in the Premier League is obvious.

"But I really hope we can get through the current window with the squad intact and have a real go at Juventus."

Auld has been amazed by the quality of the talent unearthed by the scouting network at Celtic, but he would like to see more homegrown produce come through.

He said: "The scouting network under John Park has done a tremendous job unearthing and sourcing talent from all over the globe like Wanyama, Kayal and Emilio Izaguirre. But Celtic has always been famous for bringing through its own homegrown talent and it would be great to see more of that.

"The young lad Dylan McGeough is a player I like a lot and I'd love to see him and some of the other young lads come through the ranks.

"But when you have a side that is winning like this Celtic one is then you can't expect the manager to be changing things.

"Neil Lennon has assembled a strong squad with competition for places in every position and that is very good management in my book. Sadly though I fear that depth maybe tested in the coming weeks."