Why is channel 1 not HD on sky?

Channels 1 to 5 on UK terrestrial broadcasts have been allocated as BBC1, BBC2, ITV, Channel4 and Channel 5 respectively. These channel numbers have been accepted as the norm for decades.

When cable and satellite broadcasts were first started in the UK, providers wanted to promote their own channels by using the channel 1 slot. The regulators have instructed all broadcasters to retain the traditional numbers for the first 5 channels. Therefore, HD channels must be somewhere other than those first 5 channel numbers. No doubt, this will change in the future when HD becomes the norm for television rather than the exception.