Apparently it was built in WW2 as a bomb carrier, which must have been quite some explosives, now repurposed and still gong strong as a mobile boat cradle in the yard.
There's a curious mechanism on the rear wheel (above) with what looks like a ratchet handle and gears going down to the axle, there was a cut out on the other side but looks like the mechanism had been removed, I was trying to work out if it was a brake or something else?