In a handwritten letter seen by the British broadcaster and dated 2018, Latifa asked Cambridgeshire police to refocus on the case of her sister Shamsa, now 39, who was captured aged 18 and has not been seen in public since.

Reuters has not seen the letter.

The Dubai government’s media office did not immediately respond to a request for comment.

Cambridgeshire police confirmed they had received a letter, dated February 2018, in relation to the case and that it was part of an “ongoing review”.

Latifa, 35, is herself the subject of international concern.

In a video message filmed in a bathroom and obtained by the BBC, she said she was being held captive in a barricaded villa.

The UAE last week said Latifa was being cared for at home by family and medical professionals.

The two women’s father, Sheikh Mohammed bin Rashid al-Maktoum, has rejected findings by a London High Court judge who said last year that he accepted as proved allegations that the sheikh had ordered the abductions of his daughters.

Britain has called on the UAE to show proof that Latifa was still alive.