Production house Yash Raj Films has taken over four streets around Shepherds Bush to shoot a key action sequence.
"The scene we have been shooting over the last few days plays an essential part of the story," a production source revealed.
"When you are filming exterior shots on public roads, the only way to do it is to close off the whole area, especially when there are stunts involved," added the production source.
An image of lead actor Khan riding a motorbike recently leaked online from the west London location.
Veteran star Anupam Kher announced on Wednesday his arrival in London to collaborate with Chopra again. Khan and Kaif have been shooting on the film in the UK since February 22.
"Finally in London. Looking forward to working with Yash Ji tomorrow after Veer-Zaara. His passion for cinema is really infectious," wrote the actor-teacher.
The project, which also stars Anushka Sharma, releases Diwali 2012.