US actor Meghan Markle could be worth hundreds of millions to the UK Monarchy and economy in the years ahead if speculation about her pending engagement about Prince Harry comes to pass.

That's according to UK experts Brand Finance, who predict the "uplift" for clothing and homeware brands to run into hundreds of millions each year as part of a "Meghan effect".

Brand Finance CEO David Haigh told, should Markle join the royal family, she would likely have a similar effect on sales to the Duchess of Cambridge who regularly causes clothing inquiries to surge and websites to sell out in a $266 million boost in 2015 alone.

"Although it is difficult to speculate about numbers, it can be expected that Ms Markle will join the Duchess of Cambridge as a great ambassador of the Monarchy, especially in her native United States and in Canada where she has recently lived," he said.

The "Meghan effect" will likely set in one Prince Harry pops the question. Photo / Getty Images

The royal effect is estimated to provide $350 million to the UK economy in 2017, much of which is down to unofficial endorsements such as clothing and products used by the family.

In 2015, Brand Finance put the "Kate effect" at $266 million with $177 million "uplift" for Princess Charlotte and $133 million for Prince George.

However in 2017, the figure has been revised down "as the royal couple has recently made an increased effort to shield their children's privacy and deliberately dresses them in plain, retro clothes by Spanish boutique brands, often using similar-looking outfits on different occasions to minimise the attention of the media," the report said.

"Nevertheless, the commercial impact of the royal children will grow with them, when they start making their own choices on what to wear, where to go on holiday, and who to party with. The arrival of royal baby number three is also likely to help brands trading in baby clothes and care products."

Prince Harry and Meghan Markle made their first public appearance together. Photo / Getty Images
Prince Harry and Meghan Markle made their first public appearance together. Photo / Getty Images

The figures come as the popularity of the UK royal family is high amid the Queen and Prince Philip's 70th wedding anniversary celebrations, news of a third royal baby and speculation about a wedding announcement after Markle quit US drama Suits.

Brand Finance estimates the Monarchy is worth an estimated $118.3 billion to the UK economy made up of $44.69 billion in "tangible assets" and $73 billion in "intangible value".

Tangible assets include the Crown Estate, Royal Collection, including the crown jewels, and Duchy of Cornwall and Duchy of Lancaster, which provide income for the royals.
Another $42 billion comes from the amount Royal Warrants, given to brands personally used by the Queen, Prince Philip and Prince Charles, can add to exports. Tourism, trade, charity patronage, and the arts also benefit from royal associations.

In 2017 the Monarchy is said to have added $3.08 billion to the UK economy through such intangible assets as well as visits to parts of the Crown Estate such as Buckingham Palace and Windsor Castle.

The Monarchy costs $511 million per year for British taxpayers, which Brand Finance claims is a "very low expense" considering the benefits and amounts to $7.80 per person per year. The cost is expected to rise in future due to a refurbishment to Buckingham Palace.

Prince George and Charlotte are said to be worth of $100 million each to the British economy. Photo / Getty Images
Prince George and Charlotte are said to be worth of $100 million each to the British economy. Photo / Getty Images

Earlier this month, the Queen faced a backlash after the Paradise Papers revealed about £10 million of private money was invested offshore in two funds, one in Bermuda and one in the Cayman Islands. The Duchy of Lancaster said all investments were "fully audited and legitimate".

Managing director of Brand Finance Australia Mark Crowe said "support for the Monarchy in Australia is strong, but certainly not solid.

"While the constitutional debate about a republic continues, the Monarchy's popularity is increasing thanks to the younger royals."

"Irrespective of the future of the Monarchy in Australia, there will continue to be extensive opportunities for Australian holders of Royal Warrants and Coats of Arms to leverage the inherent value of these globally recognised designations."