I can't comment on MI5 but find it extremely unlikely that they would use something such as this. I can certainly state that police CID 
don't use items and gadgets such as these and rely on good old detective work!
You will not be able to buy an item such as the Leyser 2000, or anything similar in a spy shop - well not the professional ones anyway so I wouldn't waste your time looking for one. I'm not talking about the consumer electronic shops along Tottenham Court Road (for those of you who know London) and they don't sell these products anyway, but shops such as 
http://www.spymaster.co.uk which is renowned as the best in the UK.
No disrespect but on this occasion the thought process is not logical.
 
			Member of the Magic Circle & The 2009 British Isles Close-Up Magician of the Year
It's not really an optical illusion - it just looks like one!