Six-year-old Khaleesi was named for the title taken by Emilia Clarke’s character Daenerys Targaryen in the fantasy TV show, which was still airing when she was born.

She would have been no more than a year old when the show’s critically-panned final season saw Daenerys go mad with power and become a ruthless mass murderer, precipitating her downfall.

Mother Lucy, 39, told the BBC that a family holiday to Disneyland Paris was ruined when the UK’s Passport Office refused to issue a passport for Khaleesi.

A letter from the Passport Office claimed that “her name is trademarked by Warner Brothers” and a passport would only be issued if she had “a letter from Warner Brothers to confirm my daughter is able to use that name”.

Lucy subsequently consulted solicitors who established that the trademark for Khaleesi extends to goods and services, but not names of people.

The Passport Office has apologised and said it wrongly applied guidance which only extends to people who change their names in adulthood.

“We can confirm the application is being processed and apologise to the family for the delay,” the Home Office said.