Found this on another website (moneysavingexpert.com actually)
Apparently if you book train travel online from now until 1st Sept, you get it half price.
I know it's the Scotrail website but I think you can book English journeys too.
I've just booked for myself, my mum and my ds from Edinburgh to Leeds in October for just over £28, which I thought was a great bargain.
Finally, if you're booking, the 50% discount doesn't actually show until almost the end, page 6 of 7 I think.