Needing help, entry as army officer.

[tequila]

Find yourself a good surplus military rucksack. Not sure what the British Army uses, but I'm sure you can find a similar pack on Ebay or here maybe. Also get yourself whatever the British Army is using for boots nowadays, some good hiking socks, and throw about 45 lbs. in there to start, then start road-marching yourself. Build up weight and distance as you go.

Humps suck and really just break your body down, but it's great mental training. Knowing you can do a 25k hike with a 95 lb pack in 4 hours makes actually doing it much easier. But don't do it all at once, definitely build yourself up or you will hurt yourself badly. Note: your feet will be destroyed after each hike, this is not an every-day activity. More like every other week or so. What works for me is putting on a dress sock, then a heavy boot sock over it. Blisters and hotspots will still form, but less so.

Also, do crunches and pushups every night. Max out 3 sets before you go to bed or when you wake up in the morning. Aim for whatever the max is for whatever you are shooting for --- situps especially, there is no reason in the world you cannot max this in two weeks.