Her shopping list included three shirts with size 18 collars and double cuffs, in blue, yellow and white; a navy blue weekend suit; a single-breasted waistcoat; and a set of tails – all in size XL.
Ironically, Mr Markle chose not to attend the wedding after The Mail on Sunday revealed how he had colluded with the paparazzi to stage pictures of him being 'measured' for a suit in his hometown of Rosarito in Mexico by a fake tailor.
The 73-year-old cited ill-health for not making the trip to the wedding.
A source said: 'When Johnno walked in, the tailor said: "We've got the perfect morning suit for you as well as a summer suit and three shirts for you if you want them."
"He said they were made for Mr Markle for the Royal Wedding but obviously he never came over to pick them up.
"He said that with a few adjustments, they'd fit Johnno like a glove – and they did."
Old Harrovian Mr Spence paid £2,000 ($3841) for the items, around half the full price, and proudly wore the morning suit to Ascot.
The Duchess of Sussex may well have caught a glimpse of him wearing her father's suit as she breezed past him on her way into the Royal Enclosure on the first day of Ascot, last Tuesday.
The source added: "It is common practice for the Royals to wave at Enclosure guests as they arrive in the carriage procession and Johnno will have caught Meghan's eye, perhaps.
"He has met the Queen a few times and had dinner with her once."
Mr Spence's public relations firm JSC Communications counts Derby sponsors Investec, Chelsea Thoroughbreds and jockey Ryan Moore as clients.
Oliver Brown, established 35 years ago, is the official tailor of Royal Ascot, where a top hat and tails are compulsory for Royal Enclosure guests.
The company declined to comment last night.
