Hampstead schoolboys and their friends are thought to be the first to ever attempt a triathlon in which they climb Snowdon while playing music on an African xylophone.

Six 16 and 17-year-olds will climb the highest mountain in Wales, before cycling for 16km and canoeing across a 6km-long lake on Tuesday – all while performing a specially composed piece of music on a marimba, a xylophone of African origin.

The boys – three of whom attend University College School in Frognal – have taken up the challenge to raise funds for three organisations which provide music lessons for underprivileged children.

UCS pupil Oliver Nelson, 16, a percussionist in the schools branch of the London Symphony Orchestra, said: “Hopefully up in Snowdonia the weather won’t be quite as hot!”

Oliver’s father, Martin Nelson, came up with the unusual idea after his son and three of his friends at UCS took part in a sponsored walk while playing a marimba last year to fund Oliver’s place on the London Symphony Orchestra’s summer tour.

Mr Nelson then went a step further and organised the brutal triathlon to try to raise thousands for the London Symphony Orchestra, Camden Music Trust and Seaford Barn Theatre.

The boys will play a piece composed by musician William Carslake on a marimba, ukulele, and percussive slates.

Donate online at https://mydonate.bt.com/charities/camdenmusictrust.