Anyone know how to cope with Heathrow boredom??

Hi,

We will be traveling home from Europe on an unfortunate and
unchangeable timetable that includes sitting at Heathrow airport for 7
hours (afternoon) - not enough to really do anything, but too long to
sit and twiddle our thumbs.

Any idea what to do for 7 hours? Is there a nice nearby town to visit
for the afternoon? Is there some nice touristy place close by ??

I'm sure that we're not the first to have this problem ... so what do
people do ??

Bob T.