Seems to be a bit unlikely, they would have to drive it in shifts, I think, must be about 50k a year
To give you an idea of what is possible tho, a mate sold his 200Tdi def last year, it had 254,000 on the clock on original engine and still running ok and passing emissions.
Yes, my old Defender, one before the turbo one, had done 255,000 when I sold it. Couldn't imagine it doing that 4 times tho