I am wondering if there might be a nicer venue than the Blue Posts if it is going to be a sunny day...
Somewhere with an outside space.
Maybe somewhere near Baker Street - Same line for everyone, so no harder to get to..
I went with Griff and Natalia to this place after a visit to the opera a few weeks ago:
http://www.thevolunteernw1.co.uk/findus/ It sold decent drinks (including cask ales), wasn't too boisterous or expensive, is two mins walk from Baker Street tube and (though we didn't go out there as it was pissing with rain) has a beer garden.
It also serves food, which has to be a plus.
For Yompy it is a short stroll from Marylebone, likewise for Pete from Paddington (or three tube stops).
For Andy it is on the Bakerloo line from Waterloo, which he would have had to take to Oxford Circus anyway, and it is only two stops further to Baker St.
And for me it is direct on the Jubilee line.
Any objections?