Neil Lennon's decision to leave Celtic has been in the offing for quite a while. Only the weeks and months ahead will reveal to Lennon himself whether he has made the right move, or whether it is one he comes to regret.

For clarity, it is worth confirming that, on a number of occasions over the past 12 months, Lennon has revealed to intimates that he was thinking of leaving Celtic Park.

In January, in his Spiers on Sport column giving his hot tips for Scottish football in 2014, Graham wrote:

Loading article content

5. Neil Lennon's "itchy feet" to return.

There is no argument - Lennon has been a very good Celtic manager. He has defied many who thought him too intemperate, too undisciplined for the job. Lennon has brought craft and original thinking to the task. Nonetheless, by December 2014 he'll have been four-and-a-half years in the job. I find it hard to believe he won't desire a change of scene.

A mixture of over-familiarity with the Scottish football scene, plus a hefty degree of going through the motions with Celtic, have been principal reasons for Lennon's decision.

His love of Celtic has never been in doubt, nor his appreciation of the club's standing on the European scene. But a lack of stimulation has worn Lennon down as he has led Celtic through difficult times in Scottish football in recent years.

His job at Celtic required him to negotiate some unexciting chores. The Champions League adventure between August and December is fraught, exciting, and not without its dramas, and any manager would be turned on by all of that.

That night of November 7 2012, when Lennon's Celtic beat Barcelona in Glasgow, will remain one of the highlights of his career. It once more catapulted his name all over the British football press.

But then there was the other stuff - Celtic's grim local duties. How many more times could Lennon get himself up for trips to Paisley or Kilmarnock or Perth as he went about Celtic's bread-and-butter business? Was there any stimulus in this for him, having done it over and over again?

Much of Scottish football is pretty humdrum, and Lennon, one way or another, has been doing it for 13 seasons. He needed a change.

Ironically, the demise of Rangers, Lennon's greatest rival as both a Celtic player and manager, has probably also been a factor in his decision.

Lennon loved playing Rangers and very often rubbed his great rivals' noses in it - something which helped make him a hate-figure at Ibrox and much loved at Celtic Park. But being a Celtic manager has been considerably less eventful - and maybe less fun - since the liquidation of the old Rangers and the Ibrox club's subsequent rebirth in the lower reaches of Scottish football.

The Old Firm narrative was the greatest - and the ugliest - in the Scottish game. To have it taken away has robbed both clubs and their supporters of something deeply compelling.

It seems very obvious, with their crowds down, that many Celtic supporters have adopted the same jaundiced view of the domestic scene. It is worth repeating again: while Rangers fans have had to go through a tragic event involving their club, it is ironic that their own drama has kept them firmly tethered to the cause. Celtic, in box office terms, have lacked that desperate edge.

Lennon's job in Glasgow became pretty thankless. This season Celtic won the Scottish Premiership by 29 points - and that was while we have all been lauding the rejuvenation of Aberdeen under Derek McInnes.

In other words, few gave a bat's eyelid for Celtic winning the title - it is a given before a Premiership ball is kicked. In fact, in recent seasons, the only time Lennon has warranted strong comment was when he has not cleaned up a domestic treble, such as in his failure this season to add a cup to his league title.

In other words, it was hard for Lennon to receive genuine praise for his work at Celtic. But the criticism…well, that remained on tap.

He now stands at a career crossroads. More often than not the idea of Lennon going to work in the Barclays Premier League seemed a plaything of the sports pages in Scotland, rather than in a CEO of a club in England actually coming on the phone and offering him a concrete job.

It became more and more of an issue with Lennon, when he craved a fresh challenge, whether to sit and bide his time at Celtic, or simply walk away, with nothing definite to go to.

Some are insistent that he will end up at Norwich City, currently without a manager, and newly relegated. Lennon, however, appears to have taken a step into the unknown.

How should Lennon be remembered as a Celtic manager? I would say as a very good - though not a great - one.

Old Firm managers, no matter their club's advantage, can foul up - just look at Paul Le Guen and Tony Mowbray. Lennon, however, brought passion and some original thinking to the Celtic dugout, at a time when the club made a habit of astute signings in the transfer market.

He won five trophies in four years as Celtic manager - decent but not great going. A downside, such as this season, came when he failed to add a domestic cup to the league titles he made his own. To win just two of the eight Scottish domestic cups he went for must count as a Lennon failure.

In twice guiding Celtic into the Champions League, however, and on one occasion into the last 16, Lennon established a testament to his prowess as a manager. He succeeded where he might easily have failed.

The question now is, can Lennon further his career, or will he find the grass less green elsewhere?