Paul Terry writes:
If you have ample transfer time it may be worth considering taking
the airbus which runs directly from all four terminals at Heathrow
to Euston ...

Does the Airbus still operate? I looked for details recently via the
Heathrow Airport web site, but all I could seem to find was a reference
to National Express, and on their site, services to Victoria Coach
Station. But I may have missed something, as the web sites didn't
work well with the browser I was using.
--
Mark Brader | "The good news is that the Internet is dynamic.
Toronto | The bad news is that the Internet is dynamic."
| -- Peter Neumann

My text in this article is in the public domain.