We ordered our tickets in advance on the Royal Observatory's web site for a specific entrance time. There did not seem to be a need to order these tickets in advance. We visited just before lunch time on a Sunday in the height of the summer vacation season and there was a line of only two people ahead of us. We arrived more than an hour after the designated entrance time listed on the tickets and were told by the staff at the entrance that they do not really check the entrance times on the preordered tickets.

Came down from Westminster via the river. This place is stunning what with its museums, gardens and parks together with the importance of the site for geography. To stand on the prime meridian is hard to describe. I have never experienced the feeling like I did there of absoluteness to every one else. You will know if you go there. Spent a whole day there and Di the cutty sark as well do yourself a favour

After a little research, taking the River bus was the easiest way to arrive at Greenwich. There's a nice walk up to the Observatory, a bit of a hill, but the path is good. We hadn't pre-purchased tickets as we weren't sure of the weather so we arrived early and headed straight down the path behind the little iron gate below the courtyard of the Observatory itself and took photos on the Prime Meridian there. That started a bit of a stampede as several tour groups also waiting rushed down to see what we were doing! An amusing start to our visit. On opening we walked straight in, got tickets within 5 mins and had an enjoyable morning in the museum there. My husband & I both found it very interesting. He especially like the clocks and telescopes. We both thought it very good value and although there were lots of people there it didn't seem as crowded as we expected. Bathroom facilities were good too. Then a leisurely stroll down the hill to check out all the other things to do in Greenwich.