A 5 inch gauge braked driving truck by Ride on Railways. This is one of their devilishly clever convertible raised level/ground level jobs - you simply press a button and it converts, transformer-like, from one mode to the other, even whilst travelling at speed.
Actually that's not true. You just take the seat off and put the box body on - which has its own seat - and then you're ready to go out on the ground level track.
Complete with box body, two seat cushions and leg boards.