Anyone care to guess what this plant is?

[MrsJohnDeere]

Shot up from nothing to about 8 feet tall in just a few weeks.

Very pale green colour.

Exudes a nasty yellow stain when cut which is now all over my arms and t-shirt

Help!

Giant hogweed?

rhs.org.uk/advice/profile?pid=458

No, it's not hogweed. Much, much bigger leaves and very small insignificant flowers.

Greater celandine has yellow sap, but it's usually two feet tall, max.

No, definitely not that.

It may not be clear from the pictures but each leaf is about a foot wide.

The context of all this is that my neighbour asked me to chop it back as it was restricting his light. I've cut it down to about 2 feet high and am wondering whether to get rid of it all together.

Rice paper plant?
en.m.wikipedia.org/wiki/Tetrapanax

I'm with giant hogweed: the sap is said is to be vv poisonous so be vv careful

Castor bean?

Plume poppy maclaya Chordata. If it's happy it gets huge, it also spreads quite a lot. What you see is what you get so if you don't love it just rip it out.

Definitely not hogweed.

Not ricin/Castor oil plant - similar size leaves but much paler and less glossy.

It looks a bit like the rice paper plant so might be related, but I don't think it is that. I've googled and it looks similar but different.

Certainly a less deadly suggestion than mine!

No, not hogweed but a poppy.

Macleaya. Plume poppy. Spreads through rhizones and offshoots.

Bloody amazing though. Grows up to 8-10 ft tall if allowed.

en.wikipedia.org/wiki/Macleaya

Yes, I think it is the Plume Poppy plant. Thank you!

Guess I won't get to see the flowers this year now I've chopped it down so much. Think it will be worth moving somewhere else in the garden where it won't bother neighbours!

Yep, plume poppy (macleaya cordata). Fantastic plant!