This plant has just turned up, what is it?

MATTHEW SAYS This is a milk thistle (Silybum marianum), which is a spectacular thing. When growing in nutrient-rich soil it can reach magnificent proportions, as a rosette of leaves in year one, then sending up tall pink thistle flowers in its second year. Try to collect seeds from it if you can!

Milk thistles have very attractive leaves but beware of the prickles