(dailymail.co.uk) - Whether he is on or off Army duty, it is unusual to see Prince William bare-headed.
And this is the reason why.
Pictured leaving a nightclub at 3am, the 25-year-old prince has clearly lost quite a bit more hair from that once luxuriant crown.
Sections of pink scalp peep out between tousled blond strands apparently combed forward in an attempt to hide the problem.
The prince is said to be sensitive about his looks, particularly in the hair department, and tends to wear a baseball cap when out socialising.
The first signs that William's locks were in retreat were spotted when he
was 20 - coincidentally at the same polo ground in Cirencester where his father Prince Charles's tell-tale patch was noticed, albeit at the more advanced age of 28.
In contrast, Prince Harry's bushy ginger mop as yet shows no sign of falling foul of what has been called "the curse of the Windsors".
Most experts agree that male pattern baldness is actually passed on by the mother's side of the family. William's late grandfather Earl Spencer had a bald patch.
The elder members of the Royal Family deal with their follicular challenges in different ways.
William's paternal grandfather, the Duke of Edinburgh, makes little attempt to disguise his shining pate and Prince Edward, who first started thinning at the age of 21, also favours the honest approach.
Prince Charles, however, goes for the "combover".
There was speculation two years ago, denied by Clarence House, that Charles might have had a transplant or a hair weave when his hairstyle began to look a bit thicker.
So what are his options?
What can William do to keep his thinning locks?
Carol Michaelides, a trichologist with 40 years' experience, says there is no "cure" for genetic baldness.
But there are two drug treatments and the possibility of a hair transplant.
One of the drugs is Minoxidil, which is rubbed into the scalp. This is sold over the counter as Rogaine although the Philip Kingsley clinic, where Mrs Michaelides is based, prepares its own version.
The other is the hormone Propecia, which is available in tablet form and only by prescription.
Both are said to take at least three months to work and there are possible sideeffects.
Minoxidil can cause a rash and Propecia can cause loss of sex drive.
The drugs both cost around ?30 for a month's supply - something which should not tax the royal finances too greatly.
The chances of a successful transplant depend on the quality of hair at the back of the prince's head, which would be cut off and grafted on the afflicted region.
And finally, of course, there is always a toupee or a full wig.