[Stooky Bill]

Thing is that the BBC don't have enough services to fill PSB1 with HD.

They currently have 7 TV services on PSB1 in England, Wales and NI and 9 services in Scotland, plus the radio services. PSB3 currently has 7 services in HD and 2 in SD. The radio services on PSB1 basically require as much bandwidth as the 2 SD services on PSB3, even if you convert them to AAC.

In Scotland they wouldn't have enough space to fit all services on one mux, everywhere else it basically just fits.

But they wouldn't need 9 HD services on PSB1 as 4 are already on PSB3. The only extra ones that need HD versions are News, Parliament (although that could stay in SD), Red Button, and the two for Scotland.... although one of them is already in HD in PSB3, replacing BBC3. 

So PSB1 could just have radio, News, Parliament, RB and Alba 

The intention is to close BBC4/CBBC so if that happens the requirement is four on PSB3 and three plus radio on PSB1 .... four in Scotland