Yellow sow thistle?

Yes, sow thistle. There's a lot about this year.

Lots of plants look very similar and can be hard to tell apart. Could you show the whole plant and the leaves please? If the plant is over a foot tall, leaves are prickly and the flowers go to seed as white dandelion type seed heads it will be sow thistle though.

OOPS! Just noticed you said its over 30" tall but was too late to delete.

You can eat it when young & just sprouting up, like spinach, I have!

Unlike dandelions, true thistles, or wild lettuce, sow thistles have rounded tips to the leaves.

when you dig it out does it have an underground fleshy 'root' like bindweed? if it does then it is creeping sow thistle and any bit of this rhizome left behind will regrow several plants so be vigilant in taking it out.

I collected some seeds from a blue sow thistle a few years ago which were authenticated by Wakehurst - one of their original gardeners used to own a friend's cottage down the road where I found them. They are such as pretty colour but I've never dared grow them in case they take over.