Yes! I towed an 18 wheeler!!
I was on my way home and came along behind a a big 18 wheeler Mercedes truck, and by a few minutes we hit a hill, a big one, and the truck's tyres started to spin, more, and more, and more, until the truck slowed to 2MPH.
I swerved the wheel and accelerated onto the opposite side of the road (which hadn't been driven on for the whole day) which had 15" of snow on it (the RR didn't even spin slightly I may add), slipped infront of the truck, and stopped.
I asked if he wanted a push, he said yes, so I got my tow rope out of the boot and connected it up. Got into the RR, slipped into Low-Range and signalled the driver to engage 2nd and lightly accelerate, enough to spin the wheels, but not too fast to bog down. I slowly eased in the accelerator, and in 5 seconds the RR reached 5MPH on the speedo, I thought either the wheels were spinning of the rope had snapped as I honestly didn't think my 4X4 could tow a truck!
But I looked in the mirror and low and behold the truck was moving too, with a very happy driver at the wheel! In a few more seconds the needle crept up to 10MPH, then 15, then 20. So I kept at a steady 20MPH until the road leveled out, stopped, and took the rope off, happily received £20 from the driver, and got on my way!