Knotso wrote:
Hi all and have patience with a newcomer.

I'm visiting London in a month -- for the first time -- and
staying with a friend who lives in Greenwich. Pondering the
tube map from Heathrow, it appears to be something like a
2-hour ride from the airport, to Green Park, to the Jubilee
line to South Greenwich. But then, I have no benchmark to
judge how long a ride it really is. Can anyone provide an
estimate?

Allowing two minutes per station gives a reasonably accurate journey time.