Security are said to have found a bracelet in the unnamed woman’s handbag after she was challenged attempting to leave the Piccadilly department store.

At the time of the alleged incident she was being watched because she previously helped herself to make-up samples.

The aide was monitored during a visit in September to the store’s second level – the Georgian-inspired beauty floor – by security with body-worn cameras. It is understood she left and walked down a flight of stairs, heading for a side exit.

When stopped, it is claimed she said there had been a misunderstanding, but was informed the alleged theft had been captured on film.

Buckingham Palace and Fortnum and Mason have declined to comment about the incident which sources described involved an “utterly faithful and indispensable aide to the Royal Family”.

The alleged incident is said to have caused “surprise and disappointment” at Buckingham Palace.

It is claimed the official has remained in her job and is not expected to face disciplinary action.

Fortnum and Mason, the 316-year-old store in central London, is best known as a purveyor of fine food and drink and its hampers are legendary. The store holds two Royal Warrants. One was granted by Queen Elizabeth, the other by King Charles. It also sells other luxury goods.