According to a report in UK satirical magazine Private Eye, Scotland Yard has begun a major incident investigation into the death of Chang, who was one of a number of Abbey employees interviewed by Kroll over the contents of an anonymous letter sent to Abbey chief executive Luqman Arnold earlier this year.

The letter, several pages long, was apparently compiled by Abbey staffers unhappy with the progress of a major overhaul of the bank's treasury department by respected City IT consultancy Buttonwood Tree Group. The document confected a series of coincidences, untruths and unfounded gossip about purported relationships between Buttonwood Tree, IT supplier Wall Street Systems, and senior IT staff working on the project, and spun them into a major conspiracy theory alleging serious improprietaries in the management of the project.

After an internal investigation found the dossier to be without foundation, Luqman called in corporate investigators Kroll Associates to root out the authors. Chang was one of the first to be called for interview by Kroll. He is understood to have fallen to his death from the fifth-floor balcony of Abbey’s London headquarters after requesting a break in the interrogation.

While suicide seems the most likely explanation, Chang’s widow – who according to Private Eye works for the Financial Services Authority – has been pressing for a full inquiry into the exact circumstances surrounding her husband’s death.

News of an expanded investigation by Scotland Yard couldn't come at a worse time for Abbey National as the bank prepares for its forthcoming nuptials with Spanish suitor Banco Santander. Staff morale - particularly in the treasury and IT department - will be one of the first tasks Abbey's new owners will need to address.