Owners of two M&E firms involved in the contracts for cash scam were also each jailed for 18 months for making corrupt payments to Ronald Harper, the former deputy property manager within the Royal Household.

Harper worked with an annual budget of £2.3m in the role and was able to authorise orders worth up to £30,000.

The bribes secured lucrative M&E contracts for Melton Power Services and BSI Nordale in Buckingham Palace, the Queen’s Gallery, St James’s Palace and Kensington Palace.

MPS also renewed its Royal Warrant during the period of the conspiracy.

During two trials covering the case at Southwark Crown Court, the jury heard that the former MPS director Steven Thompson and BSI Nordale director Christopher Murphy made the payments to obtain or retain the valuable contracts.

In sentencing, the Judge said that Harper’s offences were aggravated by the fact that he proudly displayed an award for excellence, given by the Royal Household, in his office.

Both MPS and BSI inflated the price of contracts and the additional amounts were then used to create a fund from which the bribes were paid. Thompson, the former owner of MPS, also kept some of the additional money himself.

Harper received £55,000 in covert payments from MPS and £20,000 from BSI Nordale. In addition unexplained cash deposits into Harper’s bank account in the region of £30,000 were also uncovered.

Nick Vamos, Head of Special Crime at the CPS, said: “This was a complex scam but by working in close liaison with Leicestershire Police, CPS prosecutors were able to meticulously piece together a case that laid bare the extent of the defendants’ corruption.

“It was a long-running, sophisticated and well-planned fraud in which they exploited the good name and status of the Royal Household to enrich themselves at the taxpayers’ expense.

“This case demonstrates the commitment of the CPS to hold to account those who seek to gain through corrupt practices.”