The Defence Evaluation and Research Agency (DERA) was a part of the UK Ministry of Defence (MoD) between 1995 and 2 July 2001. At the time it was the United Kingdom's largest science and technology organisation. It was regarded by its official history as 'a jewel in the crown' of both government and industry.
On its disolution, DERA was split into two organisations, ene becoming a commercial firm, QinetiQ, and the other becoming the Defence Science and Technology Laboratory (DSTL).
The above is based on this Wikipedia article which has links that give details of QinetiQ and also DSTL.
DERA does not seem to have had a logo.
The given webstite leads to the current government website for DSTL.