Prince William goes on leave ahead of birth

London - Britain's Prince William has gone on leave from his job as an air ambulance pilot after completing his training early, royal officials said on Tuesday, days before the expected birth of his second child.

A spokesperspn for Kensington Palace, William's official residence, said his next round of training was due to begin on 1 June.

"As he now will not have any further training to complete after returning from paternity leave, he will not return to duties with Bond (his employer) until that time and will remain on unpaid leave until then," he said.

Prince William's wife Kate is expecting their second child this month. The boy or girl will be fourth in line to the throne after their first child, Prince George, who was born in 2013.

The prince took up his new job in March but will only start flying rescue missions later this year.

He is reportedly to be paid an annual salary of £40 000 but will donate it in full to charity.

He is thought to be the first royal directly in line to the throne to work for a civilian employer.

Experts say the royal birth could inject tens of millions of pounds into the British economy, and a baby princess would give an added boost in the years to come.

"If it's a girl, it's like an investment that is going to pay off for the media and designers," Joshua Bamfield, director of the Centre for Retail Research, said after conducting a survey of retailers.

Bamfield said he expected a boost of around £80m - two-thirds coming from food and drink sales to celebrate the royal birth and a third from souvenirs.

Bamfield's centre has conducted similar studies in the past on major events in British life like Queen Elizabeth II's Diamond Jubilee and the 2012 Olympics.

It calculated the economic impact of Prince George's birth at £247m.

Catherine Hudson, Prima Baby magazine's beauty and fashion editor, said Prince George had already given the baby clothing industry a boost.

"We have now seen the George effect and are likely to see the same thing happen after the second child arrives. More so I would say if it were to be a girl," she said.

The Royal Collection Trust has already announced it will be selling an official range of baby souvenirs, while a range of private companies will also create commemorative mugs and T-shirts.