After leaving school, Grylls briefly considered joining the Indian Army and hiked in the Himalayan mountains of Sikkim and West Bengal.[19] Eventually, Grylls joined the Territorial Army and, after passing selection, served as a reservist with the SAS in 21 SAS Regiment (Artists) (Reserve), for three years until 1997.
In 1996, he suffered a freefall parachuting accident in Zambia. His canopy ripped at 4,900 metres (16,000 ft), partially opening, causing him to fall and land on his parachute pack on his back, which partially crushed three vertebrae. Grylls later said: "I should have cut the main parachute and gone to the reserve but thought there was time to resolve the problem".[20] According to his surgeon, Grylls came "within a whisker" of being paralysed for life and at first it was questionable whether he would ever walk again. Grylls spent the next 12 months in and out of military rehabilitation at Headley Court[20] before being discharged from his medical treatment and directing his efforts into trying to get well enough to fulfil his childhood dream of climbing Mount Everest.
In 2004, Grylls was previously awarded the honorary rank of lieutenant commander in the Royal Naval Reserve;[21][22] and in 2013 he was awarded the honorary rank of lieutenant colonel in the Royal Marines Reserve.[23]
On 16 May 1998, Grylls achieved his childhood dream climbed to the summit of Mount Everest, 18 months after breaking three vertebrae in a parachuting accident.[24] At 23, he was at the time among the youngest people to have achieved this feat. There is some controversy around whether he was, as claimed, the youngest Briton to have done so, as he was preceded by James Allen—an Australian climber with dual British citizenship who reached the summit in 1995 at age 22.[25][26] The record was since been surpassed by Jake Meyer and then Rob Gauntlett who summitted at age 19.
To prepare for climbing at such high altitudes in the Himalayas, in 1997, Grylls became the youngest Briton to climb Ama Dablam, a peak once described by Sir Edmund Hillary as "unclimbable".