Bungo,
Sorry to hear of the attempted "taking and driving away". Shame you didn't have a garden rake to hand to pummel their sculls with (then dump in river or canal)
Trust you have reported this to your local plod to get it "on the record"?
After the spate of reported thefts, earlier in the year, I bought a Barracuda wheel clamp (ex-Camper) from eBay for my Traveller[frame]

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Not a great picture, but a virtually new clamp - just had to add the quality padlock.
This clamp had not been messed with and came with all the adjuster bolts (hex headed) and the correct Allen Key.
After getting my 4-door, I got another one (again from fleabay)[frame]

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but this one wasn't as "clean" and some bright spark had welded over the Hex headed bolts so that you cannot take them out to adjust width!
Welding over was totally unneccessary as you cannot get an Allen key (of any bend shape) between the tyre and the bolt head (unless you cut the tyre off, but then the car becomes undrivable).
As it happens, it fits a 155x14 tyre quite well (what came fitted on the car). These Baracuda clamps are width adjustable (when not adulterated) and, as you can see in the photo, it has a coverplate that stops anyone removing the hub cap and the road wheel nuts/bolts underneath.
To remove would require a petrol angle-grinder - large bolt cropper to take of the padlock won't fit in the ironwork frame.
The cars also have a "secret switch" and steering wheel/clutch pedal locking devices.

'50 Low-light with 918 Side-valve engine,
'51 High-light with Side-valve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.