Not a salvia but what is it ????

Hello. At the end of last season I bought two plants labelled Salvia. They weren't in flower when I bought them but I planted them in the border last July. To be honest, I didn't really notice if they flowered because I was really busy with babysitting and trying to sort out all my pots. This year I noticed that one of them had died so I dug it up. The other one has now flowered and is definitely NOT a salvia. I've no idea what it is. I've posted pics and would be very grateful if anyone knows what it is. There's a few Alchemilla near the unknown plant, the flowers are very arching and yellow. Thanks for looking.