Shakespeare’s Globe Theatre does Monday tours and sometimes has rehearsal viewings. You might get to see actors fumble a line or trip over a prop—live theatre in its rawest form. It’s hilarious and humbling.
The National Gallery is open until 9pm on Mondays. Evening art hits different. You can stand in front of Van Gogh’s Sunflowers and feel deeply emotional, then walk to a nearby café for a warm brownie. That’s a perfect night.