Looks like a euphorbia to me. The sap is irritant so be careful if you have to handle it.

Hi, welcome to GoY, I agree with Urbanite, it is a Euphorbia, but can't recall which 1 at the moment, I think it's 1 that is treated as a weed here, Derek.

Caper spurge.....Euphorbia lathyris

That's the one, thanks Badfish, Derek.

and if you don't want it it's a weed. a weed is any plant growing in the wrong place. so Barley in a wheat field is a weed. though barley is a useful crop in it's own right.

I had these growing in my front garden when I moved here 20yrs ago. They are still popping up around the neighbourhood and I get the odd seedling which I dispose of. When the seeds are ripe they 'pop' all over the place & grow very easily.

Cheers SBG!

Thank You all :-)