Ed, you could correct me, but I think that is False Acacia, also known as Black Locust or Robinia. Native to the south east of the USA and widely planted by the Victorians as they had a fetish for ornamental gardens. Managed to rescue about five tons of the stuff from two felled trees from our local ornamental gardens, trees were about 150 years old and we're planted by the railway company as compensation for the lost common ground when they pushed the railway from kings cross through hitchin en route to Scotland