The Enviro400 was introduced in 2005 and has become a popular model among bus operators around the UK, as well as in Hong Kong. Initially available as a diesel, the model was adapted to a hybrid example known as the Enviro400 H. With a small change in body style introduced in 2009, Alexander Dennis Ltd relaunched the Enviro400 in 2014 as the Enviro400 MMC. A year later a third version was constructed, this being named the Enviro400 City. This latter model was originally constructed for use in London though there were sales in other towns and cities across the UK. The Enviro400 has become a familiar sight on the streets of London.