Jennifer Lopez's engagement ring: J.Lo's £3.8 million diamond stunner was made by a London jeweller

The £3.8 million diamond engagement ring worn by Jennifer Lopez was supplied by a Knightsbridge jeweller in a major coup for London, the Evening Standard has learned.

The star of Shades Of Blue and Maid In Manhattan, better known as JLo, has been sporting the emerald cut ring since she accepted a proposal from former baseball player Alex Rodriguez in the Bahamas this month.

However, despite feverish speculation in the jewellery world, little was known about the ring’s origins, until now. It has emerged that it was sourced from the Samer Halimeh store, close to Harrods, by a “middle man” acting on behalf of Mr Rodriguez.

The huge diamond, thought to be between 20 and 25 carats in size, was shown to the representative of the 43-year-old former New York Yankee, nicknamed A-Rod, as he toured the world to view the best available on the market, according to industry sources.

Once selected, the stone — described by one jewellery expert as “one helluva huge diamond” — was set in a platinum ring with eagle claws by specialists working at the store and in other workshops around London. Beirut-born Mr Halimeh is known as the “red carpet jeweller” whose A-list clients include Naomi Campbell, Oprah Winfrey and Sir Elton John as well as the royal families of Saudi Arabia, Abu Dhabi and Brunei.

He opened his £10 million global flagship store — said to be the most heavily fortified in London — in 2017. The picture windows are fitted with 30mm bulletproof glass protected by “weaved steel” curtains. He chose London rather than New York — where he has his Fifth Avenue corporate HQ — to base his biggest store because of its status as the “billionaire capital of the world”.

JLo, 49, who has been engaged five times and married three times, first “flashed” the ring to her 89 million followers on Instagram nine days ago in a post that has attracted almost 5.5 million likes.

It was most recently seen when the couple went out for dinner in New York on Sunday. They have been together for two years but have not yet set a wedding date.

Mr Rodriguez was pictured with a black eye at Miami airport last week as rumours of an affair overshadowed the couple’s return from the Bahamas.

Jose Canseco, another ex-baseballer, accused him on Twitter of cheating with ex-wife Jessica Canseco, who denied the allegations. Neither Mr Rodriguez or Lopez have commented.