For an agency devoted to secrecy and surveillance, it is an embarrassing slip-up. An inadvertent disclosure on a university document has revealed that MI5 is partly behind what was meant to be a covert bug and drone research project.

Ostensibly, Imperial College’s research was to create a quadcopter system for charging remote agricultural sensors – but MI5’s participation has emerged because somebody involved stated it was the secret second funder of the programme.

Paperwork produced by Imperial initially cited the apparently obscure Government Communications Planning Directorate (GCPD) as a backer – a moniker used in Whitehall as a codename for MI5.

Alerted to the slip-up by sister agency MI6, efforts were made to ask Imperial to discreetly remove the reference, but not before it had been drawn to the Guardian’s attention. Since then, the link to MI5 has subsequently been confirmed.

Intelligence sources say while it can be difficult to place a bug, requiring operatives to…