I think it has to be an insatiable curiosity that keeps me seeking new experiences, meeting different people and seeing different landscapes. And my obsession with linking histories together and thus having a much greater depth of knowledge and understanding of our own history, is what keeps me going on and on.
I really started long-haul travel at the age of 60, and have never stopped since. I sometimes travel with my daughter, which is a double bonus, as we have the greatest fun together.
I have also met up with my son in the Near East and had the most sensational journeys there, sometimes with a friend who is extremely compatible.
But I sometimes go alone with a view to later linking up with a group going to the same country that I want to visit.
And with all of this mix, I have had great, unique experiences.
My first unforgettable trip was with my daughter to Mexico, where we decided to do it alone and use the local buses for our inland travel.
We had a very good idea of where we wanted to go, as some years ago I had to take the place of a colleague who was organising a tour to Mexico for a highly prestigious group when she became ill.
I, who had never been to Mexico, made a room in our house into a floor-covered area of maps, information, history and buildings dealing with Mexico – I did the equivalent of a PhD on Mexico in a month.
So with this in hand we proceeded to the local bus station in Mexico City and decided to take the second-class bus because it stopped in tiny villages on the way and was very much used by the local people.
The driver used to sustain himself by getting three-course meals on the way, that he magically managed to eat while driving on the most precarious roads.
And up we went into the highlands, the homeland of the Mayans, and went off on a long ride through the countryside. We talked with everyone and had a wonderful time.
My next memorable trip was to Cuba in 2003, when I joined up with a group of naturalists from Canada who were going there for birding and botanising.
I arrived in Havana the day before the rest of the group and spent an afternoon wandering around this faded beauty of a city.
I talked to everyone – it did help that I spoke Spanish – listening to music in the streets and in cafes, and feeling utterly delighted.
And then off we went to the wild and remote places. We went through mangrove swamps by small boat, into dense wooded areas and on to islands on the Coral Reef.
Snorkelling by the boat, I thought I had come upon the true Garden of Eden.
There was fun to be had by day and night. We saw salsa dancing everywhere, not forgetting the rum in every possible variety of cocktail.
For my 70th birthday my family presented me with a holiday in the Galapagos, sailing in a tall-masted ship around the islands.
Of course, being the Galapagos, I got to swim with turtles and Galapagos Penguins, and shouted with delight when a shark appeared in the sea below.
All of this was followed by a week in the Amazon rainforest lodge, run by the local tribe, who taught us of the many sacred trees and the rituals associated with them.
Because you need to be in the whole of your health to travel with him, as it is a continuous state of going with the flow.
It was particularly beautiful to be in a magnificent Byzantine church covered in snow. And we had it all to ourselves.
I went back again and again. The final time was in 2010 when I drove with my son into the Palestinian area of Damascus for a magical rooftop dinner with his friends.
On our drive through the countryside we picked up people everywhere to give them a lift to their village, and were almost dragged out of the car into their houses.
We climbed up a mountain in the heat to arrive at an extraordinary monastery full of frescoes, where Muslims and Christians are welcomed, and a monk produces a nest of tiny birds from under a crevice and holds them gently in the palm of his hand.
We swam into Turkey because we did not have visas, and there we met with a lovely group of Kurdish young people who shared their food with us.
And then to Iran for an unforgettable two weeks. This time I was invited by the President of a Canadian agency who I had done work for in Ireland.
I had been warned not to make eye contact with any man while there.
So on day one when I arrived before the rest I went out in the beautiful park behind our hotel with eyes downcast and walked through this Persian garden of complete beauty.
Then my downcast eyes fell upon a group having a wonderful game of table tennis, and, forgetting the warning I had been given, raised my eyes and engaged with the players, who invited me to play with them, which I promptly did and enjoyed every moment of it.
Wandering through this amazing country, I talked with everyone, walked through exquisite gardens, lay underneath domes of Mosques and felt like crying at the sheer beauty of it all.
And when that part of the world was no longer possible to visit, I went with my daughter to Cambodia for more than two weeks, having made a conscious decision to visit just one country.
Rubbing noses with a stone-carved image of the Buddha in Angkor Wat when we visited the temples almost on our own, we also saw real charity at work in the form of restaurants set up to employ and train former homeless people.
There was inspiration too in the form of people who had been blinded by landmines providing massages. Craft centres empowered the local people with free literacy classes and IT classes after school.
And amid the terrible tragedy of Cambodia's recent history, one had the feeling that this country, which had lost such a high proportion of its educated young people, was on the move upwards.
The bicycle ride across a slanting bamboo bridge stretched over the Mekong Delta, made me want to live forever on that island – so terrifying was the thought of the return journey. Not to forget the unmissable ride on a bamboo-constructed train, with the sun dropping into the river beside us.
The following year it was Burma, just after the election of Aung San Suu Kyi, where I found out that her father had learned all of Edmund Burke's speeches off by heart at university. So there was an Irishman who was at the heart of the Burmese revolution.
We stayed at one point in a hotel on stilts in the water, and rowed silently among the floating gardens, where you could pick fruit just by reaching out from the boat
Beside us, the fishermen were sweeping the river with their large curved nets in a series of balletic movements.
The final trip of this year was to Ethiopa, somewhere I have wanted to visit for a very long time, and it was amazing.
I went with my daughter and two other couples, unknown to us beforehand, and travelled to the rock churches with their Coptic frescoes, which were at times so very similar to our Book of Kells.
One day, a group of local young people come up to me and proceeded to feel me all over, just to see what exactly it was that I was made of.
We made the 4,000m trip up the Simien mountains to walk among the lion-like Gelada Baboons and through amazing vegetation on paths at the edge of cliffs.
There are indeed places you can travel to on your own very successfully and very happily and others like Iran, Burma and Ethiopia that is almost impossible to do in this way.
And I love just being planted into a strange group of people and seeing what comes out of it.
I would never be put off by the idea of connecting with a group of strangers, as long as we shared a common passion, be it botanical, historical, art or whatever.
I have often shared a room with someone from another country who I had not known beforehand, and it has, to date, always been a great success.