Mysterious yellow

I've no idea what this plant is, but something had a lovely smell around here and I think it came from this. I visited my favourite city picnic spot at lunch - Middle Temple Gardens. While I was chatting to Dad on the phone about the referendum and the extra shenanigans mooted by Westminster, the gardeners' cocker spaniel trotted by. It's had a fur cut and looked very sweet. However, it's immune from saying hello to anyone and acknowledges only the gardeners.