CJ SIMS' experience with the Royal Family is not unique. Contractors and consultants that have worked on other projects for members of the Royal Family say they can be hard-nosed in their business dealings.

One QS that failed to win a project to refurbish the Queen's Gallery two years ago said at the time: "You are almost expected to lose money on a project like this – the implication is that you are letting down the Queen if you don't cut fees for the honour."

The view was confirmed by another leading QS that has worked on a number of royal projects in the past two years. "There is a cachet working with the royals, but I think they are hard-headed. If they overspend on a project, it gets a lot of press coverage and they don't like that."

He added: "Their press office is also very involved throughout the life of a project. If there are any variations and cost increases they have to be involved, even if it is tiny money."

Sims has worked on a number of royal projects over the past five years, including work at Windsor Castle and Buckingham Palace.

It was awarded a royal warrant in January.