I have mentioned it several times, but by the name Liverail. That's their internal name for this bit of their site, but turns out to be a useless search term. Officially, Charlwood House call their public services "Open Rail", while their site as a whole promotes their software products. Confusing, huh?
Here's a list of people working in this area of open rail data, most of them from public service sites, which may help in finding them.
While the longer history is useful, the main advantage is that it shows the data feed as is, without interpolating reports (as
RTT» does). It also shows more accurately what really happened when it's not as planned, within the limits of the data fed. And it shows reports from a diversion, though still can't cope with movements the happen before they get put into the timetable. But it's not pretty - which is an advantage, for some of us!