Locke Lord has been hit with a record £500,000 ($656,018) fine from the Solicitors Disciplinary Tribunal (SDT) in the U.K. after admitting it failed to prevent a former London partner from using a client account for “dubious” financial arrangements.

The penalty is double the previous record SDT fine of £250,000 ($328,009) handed out to White & Case earlier this year for conflict and confidentiality failures.

Locke Lord admitted four failings related to its supervision of former partner Jonathan Denton,  who left the firm in October 2015, including that it failed to prevent him from “using the firm’s client account in transactions that bore the hallmarks of dubious financial arrangements or investment schemes.”

The U.S. firm also admitted that it failed to have effective systems and controls in place to identify and assess potential conflicts of interest, and failed to prevent Denton from directing payments in and out of the firm’s client account which were “not related to an underlying legal transaction or a service forming part of the firm’s normal regulated activities.”

Denton was referred to the SDT after denying the allegations leveled at him. The Solicitors Regulation Authority also claims he misled third parties by producing false invoices and knowingly made statements which he knew to be untrue. The allegations are subject to a hearing before the SDT.

Locke Lord launched in London in 2011 following the hire of a seven-partner team from Salans. Denton, who joined the firm the following year from an in-house role at private lender Berkeley House Investments, is a financial services and banking specialist and a former partner at Mishcon de Reya, Salans and Wragge & Co.

“The matters investigated by the SRA concern the actions of Jonathan Denton and relate only to clients for whom he worked,” a Locke Lord spokesman said. “None of the firm’s other clients were affected by Denton’s actions.”

The spokesman said the firm regrets what happened, but is pleased that the SRA accepted its position that the firm and its senior officers did not act dishonestly or with conscious impropriety, or turn a blind eye to Denton’s conduct.

“After Denton’s departure from the firm—effective October 2015—and in consideration of matters that came to light, steps were taken to review existing practices and procedure,” the spokesman said. “A number of changes and improvements were made. We remain committed to ensuring that we are at the forefront of best practice, that we uphold the legal profession’s high standards, and that this situation does not arise again.”

A SRA representative said Locke Lord recognizes the seriousness of the issues and “has worked constructively with us to ensure proper public protection.”

White & Case’s £250,000 fine related to a 2014 High Court case in which the firm was blocked from acting for Ukrainian client Victor Pinchuk after it failed to identify a conflict of interest.

The SDT ruled that the actions of partner David Goldberg, who was fined £50,000 ($65,602) and ordered to pay costs of £12,500 ($16,400), “caused harm to the reputation of the profession in an area of international business.”