What is it please?

[badger]

Since none of my gardening friends can tell me I'm not feeling quite so ignorant now (I never know what plants are called :~( ) but this plant appeared in my wildflower garden and just grew and grew, must be nearly 6' tall now. Bees seem to like it which is good. I've had to stake it as it was flopping.

[SeaEagle]

HI Badger, I think the plant is White Melilot and it is shown here http://wildflowerfinder.org.uk/Flowers/M/Melilot(White)/Melilot(White).htm

[badger]

Thank you so much - how clever of you to know. Once I had the name I did a bit of Googling and it seems very unusual up here so wonder how on earth it arrived. Some passing bird maybe? There is only one other noted this far north on this site http://www.naturespot.org.uk/species/white-melilot but of course that could just be that no-one else has recorded it. I'm afraid I haven't as could not face yet another site registration for something I probably won't use again. Wonder if it will seed itself. I've just re-propped it but doubt if it would last long in a Caithness gale.