[Jon]

Keeping the Sun brand would achieve that, as it's clearly short for Sunderland in this case.

Well I’m guessing the thinking is that wouldn’t play well in Tyneside. Whereas Metro was a word associated with Tyne & Wear.

Although I’m not sure it was anything to do with the light rail system as that didn’t open for 6 years until after the radio station and for that matter don’t think it went to Sunderland for many years after that. So I guess they called it ‘Metro’ in the sense of it covering metropolitan area.