Looks like an Antirrhinum to me..Mainly used as an Annual ,but can self seed..I have found the odd one,the year after..

I would say Antirrhinum but I may be wrong .

See what others say.

yes it is a snapdragon or antirrhinum. they are usually grown as a hardy annual but infact are perennial. I have one that is 4 yrs old. I cut it back in the spring to about 6" and it goes off again. self seed freely too

Many thanks to everyone.