Holidays were spent rattling across Europe by train to stay with relations, many of whom had managed to retain royal estates and lived in style. To Romania, for instance, where his aunt Missy was Queen (she wore a tiara at dinner every evening) and where Philip’s cousin Queen Alexandra of Yugoslavia remembered ‘our nannies all cheerfully sitting down to tea with bowls of caviar’. The young boy whose own means were straitened was allowed no such extravagance. He was trained, Alexandra says, ‘to save and economise better than other children, so much so that he acquired a reputation for being mean.’ Other holidays were spent in England at Lynden Manor in Berkshire, the country estate of Philip’s uncle George Milford Haven. There he found a best friend in his cousin David, who years later would be best man at Philip’s wedding.

‘He had such unbelievable charm,’ said his sister, Sophie. ‘He had a tremendous sense of humour.’ He was also a real boy with an adventurous, outgoing personality, fond of climbing trees, forever testing himself against the elements and his playmates. ‘It was always Philip,’ Alexandra said, ‘who ventured out of his depth’ at the seaside, ‘or who rounded up other boys encountered on the beach and organised an intensive castle-building brigade.’ He was given a Box Brownie and took up photography, which remained a lifetime’s hobby. He had a boy’s interest in motorcars.

That humour his sister mentioned was of a somewhat rumbustious kind. ‘He was a great show-off, he would always stand on his head when visitors came,’ one of his sisters remarked. On one occasion, when staying with another aunt, Queen Sophie of Greece, and her sister, the Landgravine of Hesse, Alexandra recalled him releasing a sty of pigs and stampeding them through the ladies’ elegant garden tea party.

He could be kind-hearted. When a rich cousin, who was very taken with Philip, once bought him a toy, she cruelly said to Hélène’s nine-year-old sister Ria, who was stricken with a diseased hip, ‘I didn’t buy you anything because you can’t play.’

‘Philip went very red and ran out of the room,’ Hélène said. ‘He came back with an armful of his own toys, and the new one, thrust them on the bed and said, “These are for you.” ’

Philip’s early education was not notable for its classroom successes. At the age of five he was sent to The Elms, the exclusive American school in Paris. Philip rode there on a bicycle he had bought himself with savings that had started with the pound his uncle, the King of Sweden, sent him every year. His school report called him ‘a rugged, boisterous boy, but always remarkably polite’.