The Explorer isn't the only vehicle to use this axle layout - Moxy dumptrucks used an identical drive for a while (although Scammell must surely take the design credit). They'll go crazy places too, just like the Explorer :-D
In fact the dumptruck drive layout was first used by KOKUMS, a Scandinavian company. They were bought out by Volvo to get them out of the market (yes, they were good!). At some stage Kokums or at least the dumper designs were taken over by Moxy, who adopted the walking beam rear bogie. In 1991 Moxy were taken over by Komatsu - the Explorer style bogie continued in favour for some time, but I believe all now use a conventional 3 axle layout. And so the Explorer 'dumper derivative' seems to have finally passed into history!
All we need is evidence that the guy who ran Kokums had an ex Army Exlporer in his shed, and the evolutionary chain is proved!!!