I have to say I am surprised at the timing of the announcement, I expected him to stay at Parkhead for one more year.
I had the feeling he would fancy another season and another shot at getting into the Champions League, as well as looking to become one of the few Celtic managers to win a domestic Treble.
For whatever reason, he has decided that now is the right time to move on.
We don't know when he has made the decision to go. The season finished a couple of weeks ago and perhaps that might have given him some time to reflect and consider what he wanted to do.
Everyone at Celtic will respect his decision and wish him all the best.
You have to compliment him on the job he has done at Celtic and congratulate him for the success he has had over the last couple of years here.
It will be interesting to see where he comes up next and what job he takes, Neil is the only one that can answer those questions, of course.
Time will tell what his next move will be and where he wants to continue his managerial career, but he obviously feels that the time has come for him to take on a fresh challenge in new surroundings and test himself at a higher level.
The moment is clearly right for him and you would imagine he would get a job in England sooner rather than later.
Whether he has got something lined up or not, we don't know at the moment.
He has been linked with clubs for a few months. There was talk about him going to Norwich before Neil Adams was confirmed yesterday, while the West Brom and Tottenham jobs remain available.
Wherever he goes, he will go with the best wishes of Celtic and the Celtic fans because he has been a terrific servant to the club over the years as both a player and a manager.
Being the manager of a club like Celtic is not easy, and Neil has, unfortunately, had his off-field difficulties to deal with during his time as well.
When you take everything into consideration, you have to congratulate him on a job well done. He matured into a very good Celtic manager.
You do find that you grow and develop into the job and you certainly learn quickly when you are in charge of a club the size of Celtic.
He had success in the shape of the league titles and a couple of cups and he will look back at the positives of what he has achieved here.
Getting into the latter stages of the Champions League and beating Barcelona at Parkhead will certainly rank up there in his proudest moments. He will remember the success and wins with fondness.
I am sure he will go on and have a good managerial career elsewhere and he will benefit from being the boss of Celtic.
There are certainly bigger leagues than the Scottish Premiership, but there are few bigger clubs and being at Celtic will have prepared Neil for whatever lies ahead for him.
He came in at a difficult time for the club just after Tony Mowbray was sacked and has had a lot of success in terms of titles and also helping the club financially, both by doing well in Europe and by bringing in players that have then left and brought in big transfer fees.
The club is in good health on and off the park and Neil has played his part in that. When he looks back, he will be proud of what he achieved at Celtic.
The task for the club now is to hold on to key players, find the right man for the job and support him and get ready for the Champions League qualifiers to ensure we keep growing.