Launched in 2002, BBC Four is the most high-brow of the BBC TV channels. Having replaced BBC Knowledge (launched in 1999), it is available on all digital platforms. BBC Four exists to provide alternatives to the programmes on mainstream TV and thus the comedies found on this channel tend to be quite niche in scope. As BBC Four is focused on arts and factual series, it does not have much room for comedy - however, so far, it has managed to achieve a very high hit rate. The Thick Of It and Lead Balloon both started life on this channel.