Sump plug 1971 commando

What size spanner/socket is required to remove the big sump bolt fitted to my 1971 Fastback.

It looks to me to be about 1 1/2 ". But can't seem to find socket/spanners of the correct size or do I need to go and buy an adjustable spanner?

ny advice welcome.

Uk sources

1 1/2" will work. Here in the US we can get a huge box end spanner from the cheapo stores for about $10.

With either a socket or ring spanner, grinding the chamfer off helps get better contact on the thin hex.

Thanks guys
I found a 1 1/2" AF socket from this guy who seems to have a good selection of suitable tools.

http://www.baconsdozen.co.uk/index.htm

I lucked out when I bought a bunch of whitworth tools from a local dealer and decided to through a huge 7/8W X 1W tube spanner into my pile just because it was whitworth. Turns out the 1W (1 1/8BSF) fit perfectly but was too long. I cut it in half and drilled a 1/2 hole through the side to slide a bar through and now that's it's job. It measures 1 33/64" just bigger than 1 1/2" sae.