Help to ID a shrub please

Can anyone tell me what this is? It flowered in May but I forgot to take photos. Now a new flower has appeared alongside all the seedheads.

 

Google reckons -

Sesbania punicea, commonly known as Scarlet Sesban, Rattlebox, or Spanish Gold

 

Sesbania? Is it a small tree?

 

Nice. Clearly in the Pea family. Some good details here:
Sesbania Punicea from Burncoose Nurseries

Not hardy enough for the UK it seems.

 

Thank you all. It's currently in a large pot on the steps at the front of the house so facing full south and thus protected from cold winter winds. It can stay there for a good few years yet I think, unless we get a nasty beast from the east.

Very bonny when in flower and it's a good shape too. i shall save seeds just in case.

 

There are some in our County town of Silves. I got some seeds but never got them germinated.

 

I have a small plant, I grow it occasionally as a pot plant, never managed to get it to survive after it flowered, usually in year two.