London is chalk full of free or inexpensive lectures, talks, and workshops on everything from history, to politics, celebrities, climate change... you name it! FIE offers a series of free lectures on interesting or current topics, usually held in the Kensington area. Others charge a small fee and may be outside of the borough or even central London. These are also a great way to explore parts of London you might not regularly go to!
Here's a list of places to look to find something you're interested in.
College Writing Series
Home to leading speakers and artists of the Ethical Society
Institution that offers 130 free lectures to the public each year
Directory of talks at various venues across London
ISH host a number of events year-round, including a series of talks and workshops
Conversations, talks, and entertainment delivered by experts in their respective fields
Lectures on a number of topics hosted at the national library of the UK
Contemporary art gallery and presenting talks and events from and about the Arab world
Dedicated to the advancement of philosophy through discussion and research
An organization dedicated to scientific education and research