The out-going chief executive of Edinburgh City Council may be a life-long Hearts fan, and holding the Scottish Cup is one of his proudest moments, but that doesn't mean he wears the team scarf. Not even when Hearts are playing Inverness at Tynecastle. Not even when it's freezing.
But then Aitchison has made a career out of keeping his personal views private. He has walked a political tightrope for decades, with council leaders of a reddish hue for most of his tenure on one side, the rainbow shades of opposition on the other. Revealing any kind of personal preference has been anathema to the man who has resided at the top of the Edinburgh council tree for 16 years.
On Friday, Christmas Eve, he gives up the reigns of power (they will be taken up in January by Sue Bruce, formally Aberdeen council's chief executive), and closes the door on his large but minimalist office, 35 years of working in the public sector and an annual salary of around 158,500 - although he's not likely to feel the pinch as his total pension pot is believed to be in the region of 1.8 million.
So what does a man who has run Scotland's capital city for far longer than any politician has been in place, feel about walking out of Waverley Court for the last time?
"It has been such a privilege to be chief executive in my home city," he says. "I have always felt that I personally understand what Edinburgh is all about and seeing the transformation that has taken place here over the years, this city becoming the cosmopolitan place it is now, and feeling that I have been a part of that, well . . . it's been a privilege. The changes that I've seen happen in this city have been phenomenal. But what I'll miss most are the people, as cheesy as that may sound."
Change has played a major part in Aitchison's career. He joined Lothian Regional Council right at the start, was involved as the council fought against compulsory competitive tendering under Margaret Thatcher's government's plan to have more services delivered by the private sector. Then there was local government reorganisation, the new City of Edinburgh Council, the move away from committee-based decision-making, the controversy around public-private partnerships in building new city schools, the coalition politics of the last three years and now the potential move towards "outsourcing" of council services once again.
"Nothing stands still," he smiles. "I joined Lothian Regional Council four days after it came into existence through local government re-organisation and I'm leaving as there's going to be another one," he says with just the slightest hint of satisfaction that the trials ahead are someone else's.
"People will have to fight hard for local democracy and local government over the next while. I believe strongly that they should. It has changed so drastically since I first joined. We used to have so many functions which have slowly been eroded - a department of transport for one, which is now Lothian Buses. We also used to have responsibility for the reporter to the Children's Panel, but no more. Over the last 20 to 30 years there's been a seeping away of the functions of local authorities. People now have to have the debate about the function of local government and what they want it to be. People might say schools or social work are sacrosanct, but collecting the bins might be up for discussion.
"But I'm concerned and worried about a system where 80 per cent of our finance comes from central government and there's a tendency in Scotland to move things towards the centre. In all the time I've worked for the council there have been a lot of politicians who've had big ideas for local government and huge belief in what it can achieve, and that has inspired me and I hope that all political parties will find people of calibre to take the city forwards."
While Aitchison says he's always had an interest in politics, he never became party political. "For me it's always been about how the local authority can provide services, rather than anything else, but you can't function in this job without knowing what makes politicians tick. I have met so many big hitters over the years, Alistair Darling, Nigel Griffiths, Robin Cook, Malcolm Rifkind . . . people who had real belief in local government.
"That became most apparent in the late 80s and into the 90s when there were people who realised that to affect change in Edinburgh the council had to do it, not by itself, but in partnership with others, particularly the private sector. People like Eric Milligan, Keith Geddes, Donald Anderson, Mark Lazarowicz set out quite deliberately to try and form a better relationship to take the city forward.
"That was when the Gyle came into existence, the EICC, Saltire Court . . . all those gap sites finally began to disappear. RBS opted to build its headquarters at Gogar because there was a real partnership and Harvey Nichols came here too for the same reasons. Of course the private sector was where the investment came from, but without the desire and drive from the local authority, then these things might never have happened."
So what does he make of the current LibDem/SNP administration?
"I have worked with some outstanding quality politicians over the years and there's still a number in the council," he says. "And all the leaders and Lord Provosts I've worked with have been intensely committed to Edinburgh. Of the current councillors, well, half were only elected in 2007 and of the administration only Steve Cardownie had been in power before. They have had to learn how to "be" in power, how to work out a coalition, how to run the council on a 29/29 basis with just a casting vote. It's been a bit of a tall order.
"On top of all of that they've had financial difficulties, came in with a probably over-ambitious school closures policy, had the volcanic ash issue and the snow and a year of recession. I do have a bit of sympathy."
And of course, there has been the issue of the tram. He admits he's disappointed to be leaving with "unfinished business", but feels unable to speak openly about the problems given that TIE and the contractor Bilfinger Berger are about to enter mediation.
"You couldn't be chief executive and say I've had b****r all to do with it, so I've been heavily involved. I would like to have been able to retire and get on a tram, but that's not going to happen."
But what about TIE? Was it the correct body to undertake such a huge project? "Well the council didn't have the capacity to do it in-house," he says. "There was a choice about going to the private sector or an arms-length body, and I don't think the decision to use TIE was fundamentally wrong. Questions do need to be asked though about how well TIE has performed."
There are other things over which he's presided for which he may well be remembered, but would rather forget, such as the 1999 election count fiasco or the botched re-tendering of care services. For Aitchison, though ,the great moments in his three- decade long career which stand out in his memory are the winning of the Scottish Cup by Hearts (twice), shaking hands with Nelson Mandela at the Commonwealth Heads of Government Meeting in 1997 and lending former US president Jimmy Carter 10 to buy a book of Scottish poetry for his wife.
"He still owes me that tenner," he says. "I won't be 60 until February, but I'm going to take some time off, have a rest, do a bit of hillwalking and cycling, and then think about what to do next. I find it hard to imagine not working at all. I will miss that buzz every morning of not knowing quite what the day will bring."