Downsizing: Meghan Markle's pre-wedding weight loss drama

Meghan arriving at the Invictus Games reception. Photo / Getty Images

Meghan Markle has reportedly had her bridal gown repeatedly altered in the lead up to the big day after going on a pre-wedding health kick.

The former Suits star who is rumoured to have enlisted London-based design duo Ralph & Russo to create her gown, has had "at least three fittings at Kensington Palace, with the dress taken in each time", according to the Sun.

"Like most brides, Meghan has been on a bit of a health kick and has lost a significant amount of weight," a source said.

Meghan arriving at the Invictus Games reception. Photo / Getty Images

According to the Daily Mail, the insider added that Markle has asked for a $77,000 "ornate and intricate" gown that will be more of a "showstopper" than Kate Middleton's while still ticking the royal protocol boxes.

Accordingly, Markle's shoulders will be covered in St George's Chapel at Windsor, when she exchanges vows with Prince Harry on May 19.

According to sources even Prince Harry doesn't know which designer his bride-to-be has plumped for.

"He's being very traditional and wants it to be a complete surprise on the day," they said.

The designer of Markle's dress will only be revealed by Kensington Palace after she arrives at St George's Chapel in May 19 and is one of the most closely guarded secrets around the wedding day.

Design duo Ralph & Russo who made the daring black sheer evening gown worn by the former actress in her first official portrait with Prince Harry are now 10-11 odds on with bookmaker Coral to be unveiled as her dress designer.

The tradition of picking a "headline" designer for a royal wedding dress was established by Queen Victoria in 1840, when she chose a crinoline-style court dress in white silk-satin made by Mary Bettans with lace designed by William Dyce, head of the Government School of Design,

Victoria asked that the gown be made from fabric woven in Spitalfields, east London - where the area's weavers were suffering in the face of cheap foreign imports - and trimmed with a deep flounce and trimmings of lace hand-made in Honiton and Beer, Devon, to demonstrate her support for British industry.

The present Queen chose a design by Norman Hartnell, saving up her ration coupons to pay for the gown which featured 10,000 seed pearls, and a 4m, star-patterned lace train.