The oldest aircraft carrier in the world and the last of the British-built Indian Navy ships on Sunday sailed under tow for the last time, being taken to Mumbai where it will be decommissioned.The ship was accorded a grand send-off from Kochi on Sunday, after over five decades of service in the Navy. It is now being towed to Mumbai by three tugs, and the decommissioning orders are awaited."INS Viraat shares a special emotional bond with Kochi and Cochin Shipyard Limited (CSL), as she has been refitted here every time she needed repairs or periodic regular maintenance," a Navy official said.Commissioned in the Indian Navy in 1987, INS Viraat is a Centaur-class aircraft carrier, which was the flagship of the Indian Navy before INS Vikramaditya was commissioned in 2013.Viraat was completed and commissioned in 1959 as the Royal Navy's HMS Hermes and was transferred to India in 1987.Altogether, the ship has been in service for 55 years, including 27 years with the Royal Navy.It is to be handed over to the Andhra Pradesh government after decommissioning, and is likely to be converted into a museum.