I've been using TimeOut magazine and now TimeOut Online as a resource for years. Used get off the plane and buy it at Heathrow to read enroute to London. Magazine no longer exists. Now look at it online prior and during my stays.
I even get a weekly news letter. This weeks offered "16 free things to do this summer." Examples:
https://www.timeout.com/london/museums/southbank-centre
https://www.timeout.com/london/things-to-do/ride-london
https://www.timeout.com/london/things-to-do/summer-in-the-square
I encourage travelers to take a gander at TimeOut on line. It's a wonderful resource for first timers and for those of us who return to London because we can never get enough of it....AND it's not just a resource for London. If traveling one of the first online resources I look at. I always find a nugget of inside info that makes my journeys more enjoyable.
Lastly for August visitors please note if you are going to be in London on the weekend of August 27-28 the Nottinghill Carnival is an absolute spectacle! Great eye candy!! https://www.timeout.com/london/things-to-do/notting-hill-carnival-guide I'd take tube to Holland Park early, grab a nosh at Paul's and then follow the masses....