LiLo is back -- and she's not taking no for an answer.
Lohan rearranged her schedule to be in London the same time as Ronson flew in for several DJ gigs in the British city, deliberately running into Ronson at a club she was scheduled to play at Wednesday night, London's Daily Mail reported.
Ronson's crew made a swift exit when they saw Lohan approaching London's Bungalow 8 -- but it didn't stop Lindsay, who trailed Ronson and her posse down the road to the Blakes hotel, where both stayed.
'Lindsay has been quite crafty and has arranged it so she comes to London a few days before Sam and establishes herself as a force here," a source told the Daily Mail.
"Sam [arrived] in the first week in June for a series of DJing events and will be earning tens of thousands for a few nights of work," said the source, who confirmed Lohan made the trip after finding out Ronson would be in town.
Lohan even freshened up before she started spying on her ex -- she made a quick change in the Eurostar train she took from Paris, switching from a casual pair of jeans into a silk blouse.
The couple split April 4 after a fight at Ronson's Hollywood home escalated into violence, and Lohan has been trying to get her 31-year-old ex back since.
Ronson changed her Facebook relationship status from 'single' to 'it's complicated' this week, and Lohan has made several Twitter posts about her "certain someone" -- indicating the couple could be close to a reunion, the Mail reported.