Here is the vehicle the Meteorite was built to power. Later versions were fitted with a RR Diesel. I think the "wide load" sign refers to the 10ft width of the tractor itself!
This ballast tractor has a laden weight of 35 tons, and a gross train weight of 142 tons. The fifth wheel tractor, which many of us had a Corgi model of as boys, was used to carry Centurion and Conqueror tanks with an all-up weight of just over 100 tons.
The Meteorite engine has a power rating of 285 BHP by being governed to 2000 rpm, and a peak torque figure of 730 lb ft. Fuel-injected versions of this engine gave nearer 500 HP, but never went into production.
Petrol-engined Antars were built between 1951 and 1957.