Yes completly true. Also the old wax records had maps and paperwork hidden inside them. There was a whole special works department based at the Natural History Museum devising various gadgets for SOE and MI9 the escape organisation. A lot of people from Pinewood and Shepperton studios wer eemployed, set makers and model makers. Also conjouers and stage magicians, escapologists etc were consulted. Pickpockets, card sharps, forgers, those convicted of frauds, all were considered highly valuable people .