What was the first item that was transmitted?

The first screening on Channel 5 was THIS IS 5. Press description: A unique opportunity to be present at the birth of the channel. Be part of British history and join a host of stars as the blue, orange, pink, yellow and green touch paper is lit. Meet the faces of Channel 5 and enjoy a preview of everything the nation's newest terrestrial has to offer. 18.00 Sunday March 30th 1997.