c4countdown

It's fairly well known that St John's Wood is the only London Underground station not to contain any letters from the word "mackerel". What's not perhaps so well known is that there's nothing particularly significant about the word "mackerel" - the word "real" would do, or indeed any word containing the letters A, E, L and R that contains none of the letters from St John's Wood, such as "imperial" or "carefully". This site allows you to check, as well as to experiment with other words - the pastime is apparently known as "tubewhacking".

This suggests a challenge: what's the longest word that produces St John's Wood (or any other named station) as a tubewhack? Also, what's the longest word that produces any station as a tubewhack?

Do they have to be Apterous valid?

UNGUARDEDNESSES, which is Apterous valid presumably only due to the fact that mass nouns aren't listed for derivatives, is 15 letters and works for Pimlico.

I'm "cheating" though - I've been using this.

REPLACEABLE is 11 for St John's Wood.

There could be longer of course.

DANGLER is a unique one, but I think I've miss-understood the rules of this game?

DANGLER doesn't give you any stations at all. For a word to produce a tubewhack there has to be a unique station containing no letters from that word. So DANGLE gives you Bow Church.

Incidentally, I'm told that the list of stations on that site is out of date, but it'll do for now.