The Guardian obituary of Brian White, the Belfast man who served honourably but briefly as a Labour MP, included a reminder that there was a time – not too long ago – when the border between Northern Ireland and the rest of the United Kingdom resembled, at times, the type of border that people have been suggesting, post-Brexit, might exist between Northern Ireland and the Republic.

In 1974, during the earliest phase of the so-called Troubles, when the Prevention of Terrorism Act was used as a control on travel between these two parts of the UK, the 17-year-old White was asked for his passport at Heathrow on arriving from Belfast. ‘This isn’t the Soviet Union,’ he said, ‘we don’t have gulags here.’

Another traveller whose sensibilities were similarly exercised during this period was Seamus Heaney, who was once – some years before he became a household name – travelling from Belfast to Birmingham by air to give a poetry reading, and found himself required by an official to provide information, inter alia, about the purpose of his visit. One of Heaney’s many attributes was a finely honed sense of mischief. On this occasion he could not restrain it, and thought for a while before carefully answering: ‘To educate the English.’

The member of the constabulary charged with identifying doubtful characters on immigration reacted to this explanation in a way that combined imperviousness to irony with a thinly concealed suspicion of all things Irish. ‘Do you realise,’ he informed Heaney, ‘that I could keep you here for seven days?’ But the poet talked his way out of it. Telling the story years later, he said: ‘I had to explain it was a joke.’