On 25 Sep, 12:15, John B wrote:
You're right that it was the Archway to Barnet extension that had long
platforms. But there *was* some kind of crazy skip-stop overlap
arrangement planned, I think with the driver stopping 2 car lengths
beyond the station at Tottenham Court Rd - it's covered in Rails
Through The Clay, and I'll look it up next time I'm home and have time
(unless someone else beats me to it).

From Rails Through The Clay (second edition):

==begin quote==

The first nine-car train ran in public service on 8th November 1937
and was considered to be such a success that three further trains of
this length were put into operation in Feburary 1938
[...]
On the southbound morning peak journeys, the two rear cars were
reserved for passengers for stations to Golders Green or to Tottenham
Court Road. After leaving Golders Green these two cars stopped in the
tunnel at all stations to Goodge Street inclusive. At Tottenham Court
Road the front cars stayed in the tunnel and the fortunate occupants
of the last two could alight at the platform, having had a much less
crowded journey than the passengers on the rest of the train. From
Leicester Square to Kennington the two rear cars again stopped in the
tunnel and were out of passenger use.

On northbound evening peak journeys from Kennington, the two leading
cars were stopped in the tunnel as far as Leicester Square, and the
two rear cars were reserved for traffic to Leicester Square or to
Golders Green and beyond. At Tottenham Court Road the two rear cars
were in the tunnel and the (hitherto empty) two front cars were at the
platform; a similar stop was made at all stations from Hampstead.

There was full signposting on the platforms and cars to make sure that
passengers did not board the wrong car, but if they did go wrong they
could use the end doors to reach the correct position and travelling
ticket inspectors were available to help them. [...] At stations where
end cars were booked to stop in the running tunnel, the tunnel
segments were painted white and red handrails were installed to
reassure passengers that the train had stopped at a station.
[...]
An internal report of June 1939 recommended that nine-car trains
should not be extended beyond a handful running at the height of the
peak.

==end quote==

--
John Band
john at johnband dot org
www.johnband.org