In 1933 the Great Western Railway inaugurated an air service between Cardiff, Newport and Plymouth, via Exeter, using a Westland Wessex supplied by Imperial Airways. Mr. A. Phillips suggested carrying flown covers on the first flight of this service on 12th April 1933. Although the railway company was allowed to carry letters under the railway letter agreement, it was not clear whether the agreement would extend to airmail. It was agreed that Mr. Philips would carry the covers, charged at the regular railway letter fee of 3d. for an item not exceeding 2oz, as a passenger. At Newport and Cardiff a newspaper parcel label was attached to the covers, but as Plymouth did not have any the covers were hand stamped with the parcels department cachet.

The Postmaster-General subsequently agreed to the carriage of mail by the Great Western Railway's air service and the issue of an air fee stamp, starting on 15th May 1933. A week later the service was extended to Birmingham. The last mail flight was on 30th September 1933, but due to fog only between Birmingham and Cardiff.

Covers were produced, including one by British European Airways, to commemorate the 40th anniversary in 1973. The 50th anniversary in 1983 was also commemorated by the issue of covers, a facsimile of the original G.W.R. air fee stamp overprinted "1933-1983 50th Anniversary" and a label issued by the Didcot Railway Centre.

Designed by G Sawyer. Printed in lithography by Waterlow and Sons, Ltd., London in sheets of 20. Perf.: 10.