When did ITV start broadcasting?

Context: The history of ITV, the United Kingdom "Independent Television" commercial network, goes back to 1955.

Independent Television began as a network of independently-owned regional companies that were both broadcasters and programme makers, beginning with four companies operating six stations in three large regions in 1955–1956, and gradually expanding to 17 stations in 14 regions by 1962. Each regional station was responsible for its own branding, scheduling and advertising, with many peak-time programmes shared simultaneously across the whole network.

By 29 February 2016, 12 regions in England and Wales shared national ITV branding and scheduling, and, together with a 13th region UTV in Northern Ireland, were owned by a single company, ITV plc. A further two regions in Scotland carry STV branding and are owned by the STV Group.

Answer: ITV first broadcast in 1955.