(showbizspy.com) - Madonna left dancers at a London strip-club "amazed" when they spotted her watching in the audience.
The Material Girl hitmaker -- who celebrated her 50th birthday at the weekend -- reportedly paid a visit to the Secrets clubs in both Swiss Cottage and Hammersmith, where she was looking for inspiration for some new acrobatic tricks for her latest movie, Filth and Wisdom.
The flick, which is set in London, stars Richard E. Grant and features a character who is a ballet dancer but works as a stripper and pole-dancer.
A source tells Britain's The London Paper, "It was a low key visit and some of the girls couldn't believe they had one of the most famous women on the planet in the club.
"They are used to seeing celebrity men but never expected their job would allow them to meet Madonna.
"She spent four odd days and two full days filming at the venues and even roped in one of the crew as an extra in the filming.
"She showed a lot of interest in the various pole dancing tricks and even talked about learning some herself.
"She suggested that she may incorporate some of the moves in her next tour."
On Saturday night Madge celebrated her birthday with a bash for 90 of her friends at Volstead nightclub in the West End, where her husband Guy Ritchie gave a praising speech about his wife.