Madonna was Planning Surprise Appearance at Michael Jackson Shows

Madonna was making plans to take to the stage for a one-time performance with Michael Jackson at his 50-date London residency.

Despite a reportedly frosty relationship, following a planned duet that never materialized, Madonna was desperate to join the late King of Pop onstage at the 02 Arena in London.

Dates were due to start in July and Madonna was all set to be a special guest, according to her manager Guy Oseary.

In a post on his Twitter blog, Oseary says, "A month ago Madonna told me she wanted to do a surprise performance at one of Michael Jackson's UK shows."

Jackson was pronounced dead at UCLA Medical Center on Thursday after suffering a fatal heart attack.

The Material Girl singer, who is the same age as 50-year-old Jackson, became the female equivalent of the Thriller superstar as they were propelled to phenomenal levels of fame in the 1980s.

The pair accompanied each other to the 1991 Oscars, with Madonna dressed in full Marilyn Monroe mode, famously leading a less-confident Jackson down the red carpet.

Rumors even suggested the pop supercouple was an item, but Madonna killed that story by romancing Warren Beatty.