Sorry about the gender mix up Katriel - I assumed (which I shound not have) that Kati was / is a female name. Anyway, I now know and won't make the same error again.
Larceny is am american term and is generally not used in UK law, certainly not in police law which is what you need to consider in answering this question. There are several points in law in order to prove that a theft has been committed and all of these points are contained within the link given. However, this summary is not complete as it does not contain a reference to an attemtped theft which is an offence in itself and where the biggest risk for a pickpocket lies.
Butterworth's Police Law (one of the main police training references) gives an example of a pickpocket in order to expand on the workings of the Theft Act 1968 Section 3(1).
In terms of proving an attempted theft if you have someon'es wallet in your hand, there is no doubt of you having appropriated property belonging to another person and that even as an entertainer, the possession will probably be seens as having been obtained by a deception. The defence against the attempted theft relies solely to the honesty and circumstances of the appropriation. Of the three legal criteria that can be used as a defence, the only applicable one is to show that the property was appropraited in the
belief that you would have had the owners consent if he/she knew of the appropriation and the circumstances of it (in this case as a means to entertain and not permanently deprive).
This provision in the Act is concerned
solely with the belief of the accused and applies in the same manner for section 15(1) of the Theft Act 1968 in relation to obtaining property through deception. Given this, an attemtped theft will not be proved but this is why it is important to first ensure that an entertaining pickpocket first makes his presence as a magician / street entertainer known to the audience and then keeps his victim in close proximety at all times as it is these factors, and these alone that will facilitate a defence by demonstrating an honest intention.
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!