To quote http://overtheair.org/blog/about/
“Over the Air is an annual 2-day mobile developer event with a mix of
technical workshops put on by the community, a Hackathon to celebrate
programming & making as a creative discipline, and Lightning Talks
to entertain and inspire.
Now in it’s 9th year, the 2016 edition will take place on the 25th & 26th of November, at St. John’s Hoxton.”
Well worth looking at (I loved the one a few years back at Bletchley Park)