A share trader from France who racked up a €10m (£8.8m) profit using a British brokerage’s platform he initially thought was a training system is suing the company after it seized his earnings.

Harouna Traoré had opened a €20,000 account with Valbury Capital last summer after using a simulation of its trading software to practise dealing in equity futures, according to the Financial Times.

While practising at home several weeks later, on what he believed to be the simulation programme, Traoré placed €1bn of orders for securities, realising he had been using a genuine platform only after racking up a €1m loss on his position.

He continued trading in an effort to recoup his losses, which he eventually turned into a €10m profit after building up a position in US equity futures worth €5bn.

When he called Valbury a few days later to tell them what had happened, he was told he had breached the terms of his contract with the company and that all of his positions were “void and cancelled”.

Traoré is suing Valbury, owned by an Indonesian company, for the €10m profit he made after filing a writ against them in a French court as a consumer. According to the FT, the sum involved is roughly equivalent to the £9.9m revenue the company made in the last financial year.

Valbury is expected to argue that he is a professional, which would prevent the case from being tried in France, where Traoré would enjoy greater protection as a consumer.

Robert Falkner, a partner at Reed Smith, the law firm representing Valbury, told the FT: “We are familiar with the spurious allegations made by the French arcade trader Mr Traoré (a seasoned market risk analyst formerly employed by Reuters), which are strongly denied as wholly without merit and will be vigorously contested.”

Traoré’s lawyers said he had no prior experience of financial markets and previously worked at Thomson Reuters, where he sold performance analysis software to investors, before he was made redundant in 2017.

“This matter is now before the courts, so we consider it inappropriate to comment further,” Falkner said, adding that Valbury had kept the City regulator, the Financial Conduct Authority, informed.

Valbury is expected to argue that Traoré claimed to be an experienced trader in his application to open an account. He is expected to admit that he embellished his credentials.

Traoré lawyers said in a court filing that Valbury could have imposed stricter trading limits on him. They will also dispute Valbury’s claim that his trades were a clear error.