Mr Ricci, who reportedly referred to himself as the “maddest fucker on the planet”, is also known for his love of horse-racing and his penchant for tweed three-piece suits.

The trilby-wearing banker named one of his horses “Fat Cat in the Hat” and made £400,000 in one day at the Cheltenham Festival in 2016 after three of his horses won.

Aquis revenue up 500pc

Six has agreed to pay 727p per share for Aquis, marking a 120pc premium to its closing price at the end of last week. The companies said the deal will help the challenger stock market to expand across Europe.

Acquis was founded in 2012 with the aim of targeting fast-growing businesses. Brewers Adnams and Shepherd Neame, and horseracing firm Newbury Racecourse are among the companies listed on the exchange.

The group also offers trading products and has a technology division focused on infrastructure for financial markets.

Aquis, which is itself listed on the London Stock Exchange, has grown its revenue by almost 500pc since its initial public offering and posted a £5.2m profit last year.

It is based in London but has an additional office in Paris, employing 88 staff in total.

Six owns the Spanish stock exchanges, as well as operating Switzerland’s main market. It said the acquisition would help it serve customers in Switzerland, Spain and internationally.

Alasdair Haynes, founder and chief executive of Acquis, said: “I am immensely proud of the business we have built over the past 12 years. Since launching as a start-up subscription based exchange in 2012, Aquis has become a diversified multi-product European exchange group that creates and facilitates more efficient markets for a modern economy.

“This has only been possible through continuous technology-led innovation and the tireless efforts of our people.”

Bjørn Sibbern, global head of exchanges at Six, added: “We believe that combining Aquis with Six’s platform is a compelling opportunity to bring together two businesses with a shared commitment to capital markets innovation.

“The combination will add Aquis’ strong offering to our traditional primary exchange and data businesses, complementing Six’s existing growth listing segments.”