The Vickers Viscount Jet!

This one-off Vickers 663 Tay Viscount VX217 first flew 15th March 1950 It was used by the Ministry of Supply and then Boulton Paul for all types of air tests. It was scrapped in 1959.

http://www.flightglobal.com/pdfarchive/view/1949/1949%20-%201150.html