In reply to 8ace:
>
> My basic requirements are that it has to be active, fun, not obscenely expensive, and absolutely no bloody use in day-to-day life. If it's something that can be done in the cold winter months in London this would also be a bonus.
First guess, masturbation.
Second guess would be meditation and the search for enlightenment.
Both have the potential for blissfully being in 'the moment'