The plastic lid is similar to those handed out by coffee chain giants, such as Starbucks and Costa.
The lid, which looks like it could have been devised by James Bond's gadget guru Q, has been created by Bodmin-based LawMate UK.
Inside, it is fitted with hi-definition filming equipment and an eavesdropping device that can listen in and record conversations, even in a room full of people.
Investigators will be able to use the device to gather crucial evidence, and can activate it by pressing the letter H – which stands for Hot – on the lid.
The firm, based at the Mid-Cornwall town's Callywith industrial estate, has already sold more than 100 of the gadgets, which are designed to fit any takeaway cup in the UK. more
