Teen heartthrobs One Direction are set to have the more calming and sober influence of a firm of accountants advise them on looking after their ever increasing wealth.

Grant Thornton has been appointed to oversee the spending and investment of the band, each of whom have amassed an estimated personal fortune in excess of £15m - not bad for two years' 'work'.

Grant Thornton should be well placed to look after the interests of the rags to riches pop stars as they already look after many of the National Lottery big-money winners.

A music industry source told the Daily Mirror: 'Their success is quite staggering - so are the profits coming with it. The lads had an incredible 2012 and this year looks even bigger.

'Although they're all mature for their age, they are still five young boys at heart, and have all made mistakes - it's part of growing up.

'They've now been assigned a small team at one of the country's top money service providers who will be advising the boys on matters of tax, capital and investment.

'One Direction has become one of Sony's biggest draws and the label wants to make sure the guys are looked after.'

And the Grant Thornton wealth management team could well have their work cut out as band member Louis Tomlinson has already splashed out £10,000 on Spiderman and Ironman figurines as well as buying his own football team.

Liam spent £13,000 on a Hublot watch and another £3,000 on a designer Breitling. He also treated his girlfriend to a £50,000 Audi TT for her birthday.

Louis meanwhile owns a £45,000 Porsche and a £90,000 Range Rover, while 18-year-old Harry owns a £100,000 Audi R8 Coupe, a £60,000 Range Rover Sport and an £80,000 classic Porsche.