In message , at 13:34:07 on Mon, 24 Mar
2008, David Biddulph remarked:
Just watched the Poirot TV episode "Hickory Dickory Dock",
http://www.imdb.com/title/tt0182225/ London Underground interest included
the 1938 stock in pre-war red and cream livery, running in and out of
a station named "Hickory Fields". Where was the station though ?
I wasn't watching closely enough to see Tiled walls, but not a Tube -
it had a footbridge, and I think was open air or in a cutting - daylight
was visible along the running lines.

According to Barry Salter in 1999:

"Actually filmed at Arnos Grove (Piccadilly Line) with exterior
shots being shot *very* carefully either side of the bridge
where Bowes Road crosses the line.

But the train shots were at Morden according to Andy Davison in 2003:
http://preview.tinyurl.com/2wnrj8
and in May 1998:
http://preview.tinyurl.com/2tyzk9

and according to other folk in 2000:
http://preview.tinyurl.com/2v6mku

So a compromise would be "interior at Morden and exteriors at Arnos
Grove?" imdb.com agrees about Morden.
--
Roland Perry