In its 322-year history, Lloyd's of London has insured everything from the Titanic to Bette Grable's legs.

But never before has it written a policy for an American football player's hair.

The trademark locks of the Pittsburgh Steelers defender Troy Polamalu (29) are now subject to a $1m guarantee.

Polamalu's lush black curls are so renowned that the star has not cut them for more than seven years.

Although American footballers wear motorcycle-style helmets, the dangers of the sport for players such as Polamalu are clear. In 2006, he was tackled by his ponytail by Larry Johnson of the Kansas City Chiefs after intercepting a pass.

Polamalu was born in the United States but his family hail from Samoa. He was out of action for part of last season with ligament injuries — an absence that some fans believe cost them the Super Bowl. His hair, however, remained a big draw, even off the field.

When he announced that he would be signing autographs at a Pennsylvania shopping centre in March, fans immediately bought up all 820 tickets to the event.

The insurance policy on Polamalu's hair was taken out by Procter & Gamble for its Head and Shoulders shampoo brand, which he promotes.