London Evening Standard/London

The Duke and Duchess of Cambridge are enjoying a winter break on the private Caribbean island of Mustique, it emerged yesterday.

The couple have chosen to return to the tropical paradise for the sixth year in a row to help Kate relax after taking ill last month during the early stages of her pregnancy.

The visit is also timed to coincide with the 58th birthday of Kate’s mother Carole Middleton, and she and husband Michael are reported to be staying near to the royal couple.

St James’s Palace yesterday refused to comment on the “private” holiday but the Sun reported that William and Kate were staying at an unnamed £19,000-a-week villa with an “infinity pool”, games room and stunning views of the Caribbean. Temperatures on the island were 25C yesterday — 22C higher than London.

They first visited the island in 2006 — when many wrongly believed William was about to propose during their stay at Firefly hotel — and one of its most famous attractions, Basil’s Bar, was recreated at the Goring Hotel in London after their 2011 wedding.

Last year they reportedly stayed at Aurora House, which is owned by hedge fund manager Mark Cecil, who was a guest at their wedding. The island, once a favourite hideaway of William’s great aunt Princess Margaret, has about 80 private villas.

Kate, 31, who is due to give birth in July, is said to be improving since her three-night stay in hospital for acute morning sickness.

Kate was last seen at a formal engagement at the unveiling of her first official portrait at the National Portrait Gallery on January 11. However she was spotted last week shopping in Oxford Street.

Mustique’s Macaroni beach is described as one of the world’s finest. The island boasts snorkelling and scuba diving and the Firefly keeps a stable of horses for a “sunset gallop along the beach”.