Top Gear started on BBC in 1978. Clarkson was a presenter since the 1989 and would be joined with Tiff Needell, former F1 driver, who was a presenter from 1987-2001. The show reaches great success during the early 90's. Clarkson and Tiff are entertaining and informative while presenting cars while also have creating a growing fan base for the BBC program. Then something happened and Clarkson's ego grew faster than the popularity of the show. He released VHS tapes which were ok or mediocre at best. He apparently thought he was good or better than BBC's Top Gear. He parted from the Show in the late 90's, 1998 or 1999. He went to do mini series of diff programs along with more vhs and dvd releases. Clarkson even had a short lived talk show.
BBC stopped the Show in 2001 and then 5th Gear was created. Channel 5 took the same cast of the Top Gear program and began a new series called 5th Gear. It started in April 2002 and BBC saw a competitor and decided to bring back the Top Gear program. In fall 2002 while 5th Gear was entering its second series Top Gear started with a new crew, new studio, a test track and the Stig. Though they dont directly compete the two shows kinda compete for UK's number one automotive show.