AEC Militant.
 

As wonderful as one might consider the Militant to be, its weakness is the limited ability to suspend and tow:-
https://www.youtube.com/watch?v=ztS6JTJ6IJY

The design of the rear bogie suspension can be seen to demonstrate the problem (though the wheelbase and front axle weight don't help).

Our 'bespoke' custom-built 6x4 wrecker with Hendrickson rocking-beam rear bogie was similarly blighted (though it was a powerful tug - multi-speed gearbox and three-speed axles).

Yes, you'd have thought that having trialled the vehicle before purchase the Army would have identified this weakness.
They retro-fitted a Donaldson reactor to some of the trucks (mine included) at considerable expense; this allowed about an extra half ton to be lifted, however they then discovered the device was bending the Militant's chassis, so they banned its use! I wonder how we ever won the war... or did we?

I've often said that there's nothing like a powerful tug!;):)