From an early age, I'd been told that my dad's dad signed up underage, such was his ardent fervour to serve King and country. He was born in May 1900, and I was told he signed up in 1916 when he'd just turned 16, having lied about his age. The story was that the family were horrified, but pulled strings (they were well connected) to get him posted to Egypt, well away from any fighting and risk of death.
Only it turns out this was all complete and utter bollocks. I found his service records online last year, and he only joined up in May 1918, once he'd turned 18, and he saw no fighting as he was still in training by the time the war ended.
Fascinating in a way though. It seems he spent his life lying about signing up underage, presumably for the social kudos it gained him.
As for me, bollocks would I have signed up. I'm autistic enough for the whole social exclusion thing from being a conchie not to have bothered me at all, and no way would I want to be sent abroad to be shot at in the mud.