Close friends and family members agreed that we were easy to tell apart, but people less familiar with us continued to insist that we must be twins or brothers, or at least unknowingly related. We started to attract media interest and were invited on to a Channel 4 programme in which a geneticist used face-mapping techniques to determine who, out of seven sets of alleged doppelgangers, looked most alike. To our astonishment, we won, with a facial match of 90% – the kind of score identical twins might expect. We were also judged the closest match after close scrutiny from a panel of 100 strangers.

A DNA test gave startling results about our ancestral origins. A family historian used the results to plot our ethnic backgrounds and found that although we weren’t directly related, our ancestral maps matched almost exactly. However, John, who had always thought he had a strong claim to Viking heritage, was pretty miffed to learn that I’m more Viking than he is.

John and I are both fairly open, easygoing people who meet others readily, but I suspect that being so alike has helped fast-track our friendship. We rapidly assumed the sort of relationship you might see between people who have known each other for decades.