Locks that work

Beware that this is likely to be too small to use with any decent chain as it quotes "Eye i/d: 34mm".

Beware also that any home-grown solution that doesn't have a formal approval will probably not satisfy the requirements of your insurance.

Perhaps there should be another thread: "Ground anchors that work" ?
:-)

I went to a local steel merchant and just the fella with a blowtorch to knock me up a ground anchor for peanuts.

Grabbed a thick bar out the scrap bin, I suggested a shape with long bendy bits to sink into the concrete and he quickly made it how I wanted.

Sure its not a high grade of stainless, but it is very thick.