I've been a consistent attendee of the last few London meetups and have attended many more before that and this first time I've seen or heard of allegations of theft at London meetups. I do wonder who this "well known Wikipedian" is intended to be and who the "witnesses" are exactly, but I'm assuming good faith, and I agree with Jimmy and others that this is ultimately a matter for the police.
Accusation comes from the "friend" of a throwaway account. Looking at the list of accusations. Swiping a laptop would be doable but not easy and as someone who tends to stay to the end of meetups I would expect to have heard about it. iPhones tend not to be much in evidence and people just don't leave money lying around.
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