Purvis' Wikipedia entry is here, but as of the time this post was drafted (late December 2017), it was not very informative. More biographical information can be found here, but you will need to scroll down to find it.
Although he worked for a number of clients, he is best known for his railroad posters and those for Austin Reed, a clothier. Both Austin Reed and Purvis were at their peak when the posters shown below were created. Purvis moved on to portrait work and religious painting in the years following World War 2. Austin Reed went bankrupt in 2016 and its remains were acquired by Edinburgh Woolen Mill. As I write this, there are no Austin Reed stores in London.