Business groups have warned of widespread disruption if there are lengthy delays to EU imports due to new customs checks, and even possible shortages of food and medicine.

Last month an annual speech by the 92-year-old queen to a local women's group was widely interpreted in Britain as a call for politicians to reach agreement over Brexit.

Jacob Rees-Mogg, a Conservative lawmaker and keen supporter of Brexit, told the Mail on Sunday he believed the plans showed unnecessary panic by officials over a no-deal Brexit, as senior royals had remained in London during World War Two bombing.

But the Sunday Times said an ex-police officer formerly in charge of royal protection, Dai Davies, expected Queen Elizabeth would be moved out of London if there was unrest.

"If there were problems in London, clearly you would remove the royal family away from those key sites," Davies was quoted as saying.

Agencies