On the day of the special ceremony in Templemore in 1982, Mr Donnellan and his colleague Kieran Brennan were rewarded for their actions in apprehending the notorious bank robber Frank Ward.
However, they were to share the ceremony with the widows of three gardai who had been killed in action -- John Morley, Henry Burns and Seamus Quaid.
The poignancy of the occasion certainly wasn't lost on the two men who were lucky enough to be alive to enjoy their honours.
Mr Donnellan revealed: "It really was chilling. It was stressful looking at those families. I remember in particular Henry Burns' kids were so small.
"It really brought it home to me. It was lovely to be honoured, but it was even better to be in the good health to receive it."
He added: "It is a very thin line between life and death, and that's the one thing about the gardai, there is no group in the country that has paid as big a price.
"We were certainly traumatised after those events, but there was very little counselling around in the 1970s. If you asked for it, it would be seen as a sign of weakness. Now of course there is a great support system."
It could all have turned out very differently for Mr Donnellan, who was unarmed when he tackled Frank Ward after he robbed the Bank of Ireland in Stillorgan in January 1979.
His gang opened fire on a garda car, severely injuring two gardai. Mr Donnellan and his colleague Kieran Brennan then gave chase, managing to wrestle Ward to the ground. They would later discover that he had been armed with a pistol and a machine gun.
However, the prospect of what might have been is not something upon which the decorated officer wishes to dwell.
He explained: "We didn't really think about it at the time. The frame of mind we were in was that we thought our two colleagues were dead. We could hear them looking for ambulances urgently.
"So it is in that background that we were looking for these desperados in the mountains. But you wouldn't want to dwell on it."
Having failed in his High Court action against enforced retirement for senior gardai at the age of 60, it's on to a new phase for the former Assistant Commissioner.
He revealed: "I suppose at this point I'm trying to close a chapter. I said at the outset that I took the case on a point of principle. I was due to retire on June 7 but as the judgement hadn't been delivered I was in limbo for seven weeks.
"Of course it was a grave disappointment, but now that it has been delivered, that's it, it's over."
Originally from Ballymoe in County Galway, Mr Donnellan enjoyed a very distinguished career in the force since joining in 1968.
He recalled: "I had a wonderful career in the gardai. It was one big adventure and I met some fantastic people along the way. Those memories will always remain with me.
"We're certainly living in a different time now. The problems facing gardai are quite different and more complex, but I've no doubt that they'll cope."
And despite facing down some notorious armed criminals during his service, he is still opposed to the arming of rank-and-file gardai.
He explained: "I would agree with the situation at the moment, which is to arm the emergency response units. But, considering the type and style of policing that's done in Ireland, there's nothing to be gained from arming rank-and-file members.
"The resourcefulness of the gardai never ceases to amaze me. They have the ability to deal with very difficult situations."
During his years working as detective superintendent in Dublin, Mr Donnellan headed up the investigation into the murder of 17-year-old Raonaid Murray in Glenageary.
Despite exhaustive efforts, her killer has never been found.
Commenting on the case, Mr Donnellan admitted: "I suppose the Raonaid Murray was the one case I'd be personally disappointed with. But then, over the years I worked on some other murder cases that were never solved.
"I suppose that all adds to your experience. There's no point in saying you wouldn't do things differently. Hindsight is great sight. Looking back on investigations, I had no regrets about how I did them."
Nonetheless, he still wracks his brains about American Annie McCarrick, who went missing in Dublin in 1993.
He revealed: "There was a huge amount of work put in, as there was on other cases, there's no doubt about that. And I believe that many cases can still be solved.
"People may be in certain situations and they give alibis to people at a certain time, knowing that they weren't quite right. So there's always the possibility that some person will come forward and provide a vital breakthrough."
With his extensive experience in detective branches, it was perhaps no surprise that Mr Donnellan was called on to help with the investigation in Beirut into the murder of former prime minister Rafik Hariri in 2005.
Following his investigation, a report was sent on to the then-UN Secretary General Kofi Annan.
While there is no garda tradition in the Donnellan family, Martin's brother Jim also joined the gardai, and went on to serve with the United Nations in Damascus.
However, the work of An Garda Siochana has changed immeasurably since both men joined the force.
"The type of work has changed hugely since I joined. Now we have the scourge of drugs and there's no doubt that money is the root of all evil," he said.
"The gardai have always had a very high satisfaction rating from the public and that kind of acceptability was hard won by a lot of comrades of mine.
"The community are our customers now. We have large communities and big urban areas which place far more demands on the force.
"There are huge challenges, I've no doubt they'll deal with that as they're very versatile," he added.