Sweet pea interloper

Spent yesterday clearing and cleaning all the pots from my old patio garden - they've been sitting untouched since being unloaded from the moving van last November.

The below was merrily growing in the pot I had my sweet peas in last summer. I know it's not something I planted on purpose because that pot has never had anything else in it. I don't remember anything similar in my old garden to have hitched a lift up either and there's definitely nothing comparable in the new one. Any ideas on what it might be? I quite like the leaves and the growth so far so I've moved it to a plastic tub to see what it does, but an idea on what to expect would be great!

 

I get this growing around here, its a weed but not a bad one, has purple flowers if its the plant I'm thinking of, something related to toadflax.

Linaria purpurea comes to mind.

 

Both seem likely possibilities, and worthwhile saving. Guess I have some purple flowers to look forward to either way!

 

My best guesses at this stage would be Purple Loosetrife or Euphorbia wulfenii.