The Good Friday Agreement (GFA), which celebrates its 20th anniversary this week, is not a peace, but a truce. This does not mean that it has no value. Most people in Northern Ireland wish to abide by its terms; it has helped them get on with normal life. But it does mean that difference, rather than being gradually dissolved, is institutionalised. You almost have to sign up to one side or the other. A friend sends me the diversity form of the Northern Ireland civil service which, as a candidate for the service, you must fill in. Unlike some such forms, it offers no ‘prefer not to say’ option. Each candidate must declare whether he or she has ‘a Protestant community background’ or a ‘Roman Catholic’ one or neither. This is done in the name of equal opportunities monitoring. But its effect is to define and manage Northern Ireland by its community division. The Agreement is, as the shadow trade secretary Barry Gardiner says, a ‘shibboleth’, in the exact sense of that word — a way of distinguishing between two sides. The aim is fairness, but the result is the same old struggle for mastery, which is why, after all this time, the cross-community government of the province has broken down for more than a year.

You can see this in the Brexit-related row over the border. In reality, the Good Friday Agreement has almost nothing to do with it, but it is passionately invoked by virtue-signallers (Hillary Clinton this week). There are three sorts of border between North and South — the migration border, provided for by the Common Travel Area which predates the EEC; the customs border, which was removed, eventually, by EEC membership; and the military border, which was a function of security needs and therefore lasted, to some extent, even after the GFA. Brexit raises only the issue of the customs border. Neither Britain nor the Republic wants such a border, so there will be one only if EU dogmatists insist that Brexit requires it.

Last month, Nikki Sievwright died. As Nikki Ross, she was a top model of the 1960s. In the 1970s, she married David Sievwright, an officer in the 13th/18th Royal Hussars. When his regiment was posted to Northern Ireland, she enlisted in the Ulster Defence Regiment (UDR), the only British regiment permanently stationed in the province. According to her obituary in the Times, Private Nikki Sievwright was involved in an incident near the border in Co. Tyrone. Shots were fired as two cars approached a checkpoint. The UDR checked the bona fides of the cars’ occupants and the commanding officer was about to let them through, but Private Sievwright was suspicious and insisted on searching the female passenger, as only female soldiers were permitted to do. She found the driver’s passport in the woman’s knickers, and thus discovered his real name, which was on the wanted list. Following her husband in military/diplomatic postings abroad, Nikki loved riding horses into wild places, but was banned from doing so by the British ambassador in Beirut, who said her beauty made her too conspicuous when intruding upon Hezbollah territory. There is excellent raw material here for a film, I feel, and if Nikki Sievwright had signed up for the Vietcong or the IRA, I am sure it would have been made by now. But of course Hollywood would not dream of glamorising a soldier in the UDR. Someone else should do it. It could be entitled Greenfinch, which is what women soldiers of the UDR (four of whom died on active service in the Troubles) were called. If the film uses — as it should — a feminist ‘narrative arc’, it should bear in mind the fact that the UDR was the first British regiment of which women were an integrated part. In their early days, the Greenfinches had to wear skirts and knee-length boots, which must have looked marvellously filmic with Mrs Sievwright inside them.

And here is another example of bravery in relation to Northern Ireland, but touchingly unfilmic. In 1989, Ian Stewart, the Northern Ireland Security Minister, was in a helicopter in the province which suddenly had to take evasive action because of terrorist threat. He fell off his seat and dislocated his pelvis. So correct about secrecy was he that he would not even tell his wife how this had happened. The doctors told him to rest on his back for six weeks, but he refused because he was steering a piece of contentious legislation through the Commons. He dismissed the injury as part of what he called ‘the buggeration factor’. As a result, Stewart’s health was permanently damaged and he had to leave the House in 1992, after which John Major thanked him nicely by making him Lord Stewartby. Ian died last month, but unfortunately neither I, nor his obituarists, knew this little story at the time.

In my researches for the final volume of my Thatcher biography, there is plenty, of course, about the Cold War, and its end. A constant bone of contention with the Russians was defection to the West. They were particularly furious about the MI6 exfiltration of the KGB man and British double agent Oleg Gordievsky in 1985. For several years afterwards, despite persistent personal pleas from Mrs Thatcher to Mikhail Gorbachev, the Soviet Union refused to allow his wife and small children to join him in Britain. The KGB persecuted her, and told her untruthfully that her husband had remarried. The family were not allowed out until 1991. But what is striking is that the underlying conversation about wider issues between London and Moscow was well sustained. There was friction, but no breakdown of trust. Thatcher and Gorbachev continued, in her famous phrase, to do business together, and help one another wind down the Cold War. The Skripal poisoning and its aftermath reveal that things are actually much worse today. There is no constructive relationship. The Putin regime has retained all the nastiness of the totalitarian era, but lost its policy discipline, and has even less respect for international rules.