Weed of Cultivation

I discovered this thistle-like weed on the edge of a field beside Hamsey Lane while taking a scenic route home from Burgess Hill this afternoon.

I feel like I ought to recognise it - some sort of Sow-Thistle, perhaps? But when I looked online to try and identify it, I couldn't find anything with the distinctive 'spiny warts' on its leaves that this plant has.