Land Raiders from the Great Crusade and Horus Heresy (Forgeworld & Games Workshop models)

A comparison of four different versions of the venerable Land Raider. In order from left to right, they are:
Land Raider Mk I (circa '80s Games Workshop)
Land Raider Proteus (Forgeworld)
Land Raider MK IIB (Forgeworld)
Land Raider Spartan (Forgeworld)

[@jonjcc2014]

Any kind soul willing to tell me which is which? From left to right or right to left.

[@starcrusader5685]

From left to right:
1 Original plastic land raider, retconned to be ‘Proteus’
2 Forgeworld Proteus Land Raider.
3 Forgeworld MKIIB
4 Forgeworld Spartan super-heavy