The hunt for the next chair of historic British sites including the Tower of London is being scrapped and restarted - the latest in a string of failed appointment processes for major public roles.

Sky News has learnt that officials at the Department for Digital, Culture, Media and Sport (DCMS) have been told to go back to the drawing board in the search for a new chair at Historic Royal Palaces (HRP).

Ministers are said to have decided that a shortlist of prospective successors to Rupert Gavin, the current occupant of the role, was not sufficiently diverse.

A Whitehall source said the decision had disappointed candidates who had been shortlisted for the prestigious post.

Mr Gavin, a former chief executive of BBC Worldwide and Odeon Cinemas, has held the role since 2015, and is now expected to remain for several months longer than anticipated while the revamped search progresses, the insider said.

HRP is charged with managing half a dozen of the UK's most prominent venues with close links to the country's monarchy.

Hampton Court Palace.

They include Hampton Court Palace, Henry VIII's favourite residence, and Banqueting House on Whitehall, built by Inigo Jones and completed in 1622.

HRP's chair is appointed by The Queen on the recommendation of the culture secretary.

A source said the shortlist had included a number of well-known businesspeople, although they declined to provide their names.

It is the latest in a string of public appointments to be delayed because of logjams in government decision-making or ministers' dissatisfaction with lists of potential candidates.

The DCMS has been disproportionately affected by these aborted processes, including at the media regulator, Ofcom, where the search was restarted before the recent appointment of Lord Grade.

A DCMS spokesman declined to comment.