Hundreds of supporters wearing their country’s shirts, flags and kilts have been chanting, singing and playing bagpipes at Leicester Square, Kings Cross and Hyde Park.
The much-anticipated match, the 115th in international football’s oldest rivalry, is the first time the two sides have met in a major tournament since Euro 96, when Paul Gascoigne’s famous goal sealed a 2-0 win.
Scotland fan Rab Foulis said supporters were “bringing a party atmosphere” to the city and “helping London’s economy”.
Speaking near Kings Cross, Mr Foulis said he had been waiting 23 years since wanting to go to the 1998 World Cup in France, where Scotland played their last major tournament but his wife did not let him.
Ecstatic that his new wife has allowed him to go to the Euros, he said: “We waited 23 years.