Guilt, my Victorian grandad would say, was the most painful of all life’s travel companions. This week, 51 years after the old chap moved to the Land of the Hereafter, I realised the wisdom of his words.

Australian couple, Gerry and Jean, on a trip to Europe after selling their soft furnishings business in Melbourne, were taking pictures in Radcliffe Square on Tuesday afternoon. The Camera, St Mary the Virgin Church, All Souls, Brazenose – nothing escaped their antipodean shutters. I bade the couple G’day.

“You lucky b****** – living with this on your doorstep,” he said. I didn’t correct his assumption that I was born out of wedlock or that my doorstep was nearby, but agreed with the basic sentiment.

They were in Oxford for one day. They wanted to see all there was to see, but felt they were losing the battle.

The clock on St Mary’s struck 3pm and the university church became centre of our attention. I explained its role in the execution of the Oxford martyrs, adding there was a tablet inside, listing all the victims’ names.

Could they see it, asked Jean? Why not, said I.

We entered through the shop. More people were around than usual, many seated, most of them immaculately dressed. We studied the tablet and I explained who was who – or rather whom I knew to be who. She took a photograph but resisted a repeat, saying she felt under scrutiny.

It wasn’t until a smart Royal Air Force cadet thrust a programme into my hand that I realised we had gatecrashed the High Sheriff’s law lecture by Lord Mance, Justice of the Supreme Court.

“Are you visitors?” asked a man clutching numerous sheets of paper – a sure sign of authority. Gerry said they were, believing he was referring to their tourist status. Before you could say “move along please”, they were ushered to two seats in the middle of a row. Our trio was split; they were imprisoned mid-pew.

I was offered a lone seat some rows back, but declined. I signalled to the couple indicating I was leaving; an expression of foreboding crossed Jean’s face. It haunts me still.

Why did I take such an uncharacteristic step? I felt I was improperly dressed; black shirt, red silk tie and black bomber jacket were inappropriate for the occasion. Well, that’s what I told myself.

Outside I met Tom Hill, chief executive of Helen and Douglas House. He seemed pleased to see me and suggested we went in together. I declined and headed down High Street.

I knew Tom was old and wise enough to look after himself. But vanity had led me to abandon Gerry and Jean – all those miles from Melbourne...