http://www.tangoalfresco.com/
There will be some Tango parties in Regents Park this summer. Jill Barret (mentioned in the Linked page) is a friend of mine and teaches tango.
Shall we form a group to book Jill for classes and then go to Tango Al Fresco? we would need 20 plus people. Say a few sundays 12 - 4 then go to Regents Park on the last one for a dance