Plans for Welwyn Bakery, which was built in Bridge Road East can be seen at Hertfordshire Archives and Local Studies. The plans are dated January 1926.
In our pamphlet files at Hertfordshire Archives and Local Studies i came across a photocopied edtition of the ABC Guide of Welwy Garden City from 1930, which said the following about the bakery.
The Welwyn Bakery (always open for inspection) has electric ovens as well as the latest type of steam ovens. It is famous for winning awards for bread in open competition.
I can remember Sunblest Bread and the van that used to come round an deliver it.