They have to carry their backpack and if they forget it, they forget it - because there's just too much to keep track of.

They are much cheaper than other taxis, although the lone passenger can only carry a backpack as luggage.

But think about it: when was the last time you saw anyone carrying a backpack and smiling at the same time?

For much of the time he and fellow commandos carried a backpack weighing up to 85lb.

I'm also carrying a backpack filled with 100kg (15 stone 10lb) of sand and lead, to represent the weight of carrying a battle casualty.