[Radio_man]

Looking back on iPlayer, they went from a report into coverage of parliament at 15:41 (with OOV handover by Ben Brown). Though on a topical issue, I can't say it seems like a major debate going by the attendance. They continued with parliament until 15:56 (when they were closed OOV by Ben - who did said they would bring you more in a minute). Weather and TOTH sequences occured as normal, but then went into Global. There isn't a major international story this hour and there's clearly no staff shortage. Based on all this, I'd say something must've gone wrong in Studio E.

It also would not surprise me if this is a deliberate simulcast though. A technical fault in E is the most likely explanation in this case, but in years gone by, rather than just simulcasting with World during UK daytime NC hours, Ben would've quickly set up in another studio, A for instance, whilst they were broadcasting the debate in Parliament.
Instead now the default whenever there's a problem with the NC, whether it's technical or staff related, seems to be to go straight over to World.