Quick-thinking Serjeant Deacon Cutterham had just five seconds to plunge his arm into murky ditchwater, retrieve the high-explosive device and throw it to safety.
He and his patrol were wading through an irrigation ditch knee-deep in water in the Nahr-e-Saraj district of Helmand in Afghanistan on May 24 last year when the grenade landed in front of him.
Sjt Cutterham, from Bristol, said: "I heard the 'ching' of the fly-off lever coming off it. It all happened so fast but so slowly.
"I just went into autopilot. I shouted 'Get down, grenade', ran forward, grabbed it first time and just let go of it.
"I can't believe I didn't lose my fingers because as soon as I let go of it, it exploded. If I had missed it, it would have been game over."
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