Police were heard to tell anti-Thatcher protesters in Trafalgar Square that Millwall football fans had joined the demonstration and were "throwing bottles of urine" at officers.
Millwall supporters were earlier involved in crowd trouble during the club's FA Cup semi-final against Wigan at Wembley.
More top news
Theresa May outlined her objectives for Brexit negotiations on Tuesday, but what did people from both sides of the referendum make of it?
Milder Atlantic air into the north with colder, Continental air into the south.
A report produced for the British government criticised the security at the Riu Imperial Marhaba hotel where 38 people were killed in 2015.