The Solicitors Disciplinary Tribunal (SDT) has fined a former Kingsley Napley partner £15,000 for misconduct, along with legal fees of £7,500.

Matthew Duncan – who at the time headed up Kingsley's private client practice – was found to have authorised payments to a client between October 2015 and May 2016 in breach of the terms set out by a district registry, according to the case records published by the SDT.

The tribunal found that he had lost £500 entrusted to him by a separate client, for which he was ultimately responsible and which he accepted, according to the judgment document.

In its explanation of the penalty imposed, the SDT stressed that Duncan's misconduct did not arise from dishonesty but rather from "genuine mistakes upon his part rather than a deliberate decision to act with impropriety".

The SDT ultimately concluded that he "should have known better".

Duncan's client, known only as Client A, was the widow of an ultra-high-net-worth individual who was also in a dispute with her partner's children over the distribution of the estate.

She was granted the role of executor of the estate but did not have the authority to make any payments out of the estate. Despite this, the tribunal agreed that Duncan made a payment of £750,000 to her in October 2015, followed by a further six payments totalling £825,542.46 during a period of eight months from the estate, which was worth "in excess of £9 million".

Duncan, who is now a consultant at London firm Druces, was also found to have provided insufficient advice to Client A on the risks related to the payments, particularly in relation to her role as executor. Summing up the misconduct case, the tribunal noted that these payments could have prejudiced Duncan's client in her role as executor.

Explaining his actions before the tribunal as part of his mitigation, Duncan argued that he had been acting in the client's "best interests", that he made the payments to Client A on the basis that she "was without income" following the deceased's passing, and that he "honestly believed" the payments were permitted under either the terms of the grant or the Trustee Act 2000.

Arguing in mitigation, Duncan said that, as a consequence of these allegations, he "has had to leave Kingsley Napley" and has "suffered significant financial loss".

A person on Duncan's behalf said he is declining to comment on the matter beyond what is included in the judgment.

Kingsley Napley and Druces declined to comment.