Appeared from nowhere

In April we had a huge JCB clearing away some commercial kennels that were here when we moved in 16 years ago.
The area has been cleared and I hope to eventually put the area back to how it had been ie back into a grass area for grazing. The below have appeared on the area and I haven't the slightest idea what they are. The leaves are slightly hairy and the plant is about 1ft tall . The little flowers are very pretty and slightly remind me of a Salvia I have. The seed of these must be long lived as to my certain knowledge the kennels were built in the 60s and the area where these wild? flowers are now growing had about 8ft of subsoil on it since the 60s until earlier this year.

 

Large-flowered hemp-nettle (Galeopsis speciosa). It's a native annual in the dead-nettle family (Lamiaceae).

 

Thanks both. I've never seen them before (have about 8 plants appeared) either here or in any other garden I've had. Is it quite common? A friend of mine is writing a book on wild flowers and has been taking photos of many that are in my garden (ok I can't weed everywhere!).He took some lovely photos of a huge clump of Mimulus (Monkeyflower) that was growing alongside our burn (stream) and the small number of Marsh Orchids that appear. His enthusiasm and knowledge has certainly increased my awareness and appreciation of the lovely wild flowers that are around here. I will let him know I have this plant flowering atm, he may well want to photograph them and he unlike me knows how to use a camera.

 

I've not seen one before

 

I've seen it on waste ground. Don't know how common or not it is.

 

They are not super-common and I reckon you'd have to be on the lookout for unusual plants to spot one.