In "Beachhead Assault" by David Lee about RN Commandos,Sub Lt Ron Lawrence RNVR describes using an "Alligator" a "large armoured vehicle with balloon tyres, as distinct from tracks, and completely open top"
This is on Juno beach shortly after D Day
What was it or is his recollection at fault?

Not sure if this helps, but Alligator was a name for Roebling Amphibian Tractor which was direct predecessor of LVT/Amtrac. Although open on top, it doesn’t have balloon tyres.

http://www.olive-drab.com/idphoto/id_photos_lvt_alligator.php

Note that LVT(A)2 was used by British on D-Day.

http://www.6juin1944.com/assaut/amphib.php?id=18

HTH

-A-

The British Army's attempt at a wheeled amphibious truck was the Terrapin, but that didn't see service until the Normandy campaign was over.

The Wheatcroft collection has one of the few survivors of this strange-looking vehicle, which I don't think was armoured.

http://www.wheatcroftcollection.com/terrapin.html

David

Original Caption: A column of 'Alligator' amphibious vehicles passing Terrepin amphibious vehicles on the Scheldt River near Terneuzen, October 13th, 1944

Source URL: http://commons.wikimedia.org/wiki/File:Alligators_passing_Terrepin_amphibious_vehicles.jpg

It appears they operated together so perhaps he confused the two.

-Doug