Blog: She may have done more than 400 state visits criss-crossing the globe numerous times in her nearly 60 years on the throne. But today truly is an historic royal occasion as the Queen, at 85, and the Duke of Edinburgh, 90 next month, cross the Irish Sea.

This is one of the shortest journeys they might take. But it is hugely significant in all that it means.

It is a century since a sovereign – King George V and Queen Mary – has so much as stepped across Dublin’s forecourt, and today everything changes.

Despite the qualms and concerns of advisors who think the risk of dissidents and troublemakers is still great – perhaps too great to allow the Queen to make the trip at all – Her Majesty took a different view. She was determined to keep her promise to visit the Irish Republic, believing that the goodwill it will generate far outweighs the risks.

The Queen and Duke will have weighed up many visits over six decades of travelling for Britain. And it’s fair to say that on some occasions there will have been causes for concern.

The cautious will say the same about this momentous four-day visit which began today and will hopefully achieve so much. Simply by being there.

The banner wavers may be noisy but it goes without saying that the 5000 policemen on duty will also have the threat of terrorism in their minds.

This incredible royal couple have never chickened out on anything; they have rather taken the view that you meet your commitments, make sure the best security is in place but then put on your hat and go along to do your bit. They know as well as anyone and better than most that in democratic countries, you can never guarantee total safety.

As far back as her 21st birthday, the young Elizabeth suddenly and unexpectedly in line for the throne, pledged herself and her life whether long or short, to the service of the people.

In the midst of so many to remember, the visit to Ireland is another example of doing the right thing whatever the circumstances.

And as historians, political reporters, royal correspondents and the world’s press rush to comment, Her Majesty and lifelong support Prince Philip simply carry on meeting people, doing the walkabouts which the Queen made popular, that’s the bottom line.

She is doing the right thing for nation, for governments and most of all, for Ireland.