Tim, I've got more than one passion and sometimes it's hard to prioritise. Initially I was introduced to railway modelling by my Dad back in 1955 when he and Ma bought a trainset for my Christmas prezzie. It took a back seat in the Sixties and re-surfaced about thirty years ago when our first son was born. Basically it was a disjointed affair, no background knowledge at first and then specialised knowledge came with membership of railway interest groups. That sort of ties in with interest No.2, history, although my primary historical interest pre-dates the railways by over 800 years: the age before the Age of Chivalry (so-called).
A third passion is photography, although these days I only have to compose the picture - the technical side went when someone nicked my SLR.