Gresham College

I work just across the road from this place and was looking for lectures and ‘cultural events’ to go to and discovered Gresham College. The great thing about this venue is that they do lunchtime lectures. That last just long enough for you to go out to and get back to your desk afterwards. The seating is on a first come first served basis and as the other reviewers have pointed out they are becoming very popular. This is in part due to the high calibre names that they get to present. There is a lecture for everyone here. My favourites are the science and nature ones and they occur on a weekly basis.

Brilliant lectures. There’s something for everyone here.

Founded in 1597, with roots in and based on the tenets of the Freemasons, a meeting place for the original Invisible College, and precursor to The Royal Society is Gresham College.
A centre of higher learning that admits no students nor offers any degrees, Gresham College is a bit of centuries old London history that is still active, free and open to the public.
It offers regular lectures to all who are interested, in its schools of; Astronomy, Divinity, Geometry, Law, Music (sometimes including a live rendition of the music being discussed), Physic and Rhetoric.
To me this is one of the ultimate hidden gems that London offers. While the college itself is a marvel (the concept that still persists, as well as the various buildings it inhabits), the real gem is the lectures that are on offer.
Truly marvellous that some of the top professors in the country are willing to dig into their time and give public lectures about some very interesting subjects indeed.
My tastes have steered me to the lectures dealing with Astronomy, Divinity and Rhetoric, but surely there is something for everybody here. The Q&A sessions after these informal lectures are very insightful. The audience generally consists of various intelligencia as well as experts in the field being discussed, so the questions asked are very knowledgeable and only improve your understanding of the lecture.
Pros
— high quality of lectures
— interesting and diverse subjects on offer
— free and open
— good location
— lovely old buildings/​halls (one was even held in St Paul’s Crypt)
Cons
— lectures can fill up fast at the smaller venues like Staple Inn Hall and Barnes Inn Hall, so you may end up standing.