Clive Page writes:

Someone I know wants to go tomorrow (Sunday) from Luton Airport
Parkway station to Deptford. Trains to Deptford go from Cannon
Street calling at London Bridge. So this is a pretty simple journey,
really, and there seem to be three reasonable routes:

(1) LTN to West Hampstead, then Jubilee line to London Bridge.

(2) LTN to St. Pancras, then Northern Line to London Bridge.

(3) LTN to Blackfriars, then Circle/District line to Cannon Street.
Snip

I appreciate that journey planning is a complex job, but it seems to
me that the current examples do a rather poor job even in fairly
simple cases. Does anyone know of any better journey planners out
there?

I have tried inputting that journey on Google Maps, and it suggests LTN
to Blackfriars and then District/Circle to Cannon Street.