It required stand-ins, a set of blocks and four visits to Buckingham Palace, but the result was a little piece of history as stamps featuring a monarch and three direct heirs go on sale for the first time.
Royal Mail's commemorative set of four stamps, which includes the first to feature Prince George, was commissioned to celebrate the Queen's 90th birthday. And while Prince George's parents often describe him as "naughty", photographer Ranald Mackechnie said he was a delight. Mr Mackechnie said: "He was absolutely charming, as you can see from the picture. You only have a short window of opportunity with small children, but Prince George was on good form and everyone seemed to enjoy seeing him enjoy the day."
To make sure Prince George was not too far below the Queen, the Prince of Wales and the Duke of Cambridge in the picture, he had to stand on a set of high-density foam blocks brought along by Mr Mackechnie.
"He was fascinated by my lights and all the kit and he was quite happy standing on the blocks.
I took maybe 80 or 100 shots but when I saw this one I knew straight away that was it."
Mr Mackechnie, a former apprentice to Norman Parkinson, spent weeks preparing for the shoot after he was asked by the Royal Mail 18 months ago to carry out the commission. His first choice of backdrop was the Yellow Drawing Room at the palace but, after taking some test shots, he realised it was "just too yellow" so he switched to the White Drawing Room where he spent six hours over two days perfecting the composition. During one session he used stand-ins of similar heights to the Royal family, though he used a yardstick for Prince George as it was more likely to keep still than a child double.
Buckingham Palace supplied Prince George's exact height so Mr Mackechnie could work out how best to get his face on a similar level to his father, grandfather and great-grandmother. He said: "Because the picture was going to be turned into stamps on a sheet, each person's head had to be in exactly the right place. A millimetre the wrong way on the final sheet would have made the perforations too close together, so I had to make sure everyone was spaced the right distance apart.
"It would have been nice to have used a piece of furniture from the room," said Mr Mackechnie, "but it wasn't possible, so I brought along the blocks for him to stand on. I had some other ones in case he had grown since they measured him, but he hadn't."
His meticulous preparations meant he was able to complete the final shoot in less than half an hour, though disaster almost struck at the last moment.
"When the Royal family came into the room and sat down, my computer system crashed," he said. "Prince Charles was very sympathetic and saved my blushes and fortunately I had back-up so we were back up and running in about a minute."
The photograph was taken last June before Prince George had reached his second birthday and Mr Mackechnie, 55, signed a confidentiality agreement that meant he could not even tell his wife he had been to Buckingham Palace. "She still doesn't know," he said yesterday. "She will only find out when this is made public. I stuck to the John le Carre theory that if you tell one person, you've told everyone."
Royal Mail is also issuing a set of six commemorative stamps showing the Queen in her public and private roles over the past 90 years.
All of the stamps will be available from Post Offices from tomorrow.