In the midst of the casting announcement for Doctor Who series 11 that came out yesterday – with Bradley Walsh leading the three new companions that Jodie Whittaker’s Doctor will be travelling with – came a change in format of the show.

The BBC confirmed that Doctor Who series 11 will, as rumoured, be coming down to ten episodes. It’s unclear at the moment if that also includes the Christmas special or whether that’s extra. But it’s still going to be a reduction in the amount of Doctor Who that we get in a single series.

When the rumour first went around, it sounded like we were getting ten hour-long episodes, which was a decent enough trade-off. There have been more than a few Doctor Who episodes in recent times that have drawn to a close just as they’ve got going, and a bit more breathing space in them wouldn’t have hurt.

But now we learn that whilst the episodes will be extended, they’ll only be extended by five minutes. Granted, that’s five minutes that’s better than nothing, and it does give some room to do something. But not much. Save for the hour-long opening, it feels slightly like the BBC is shortchanging Doctor Who here. Just a few series ago, we were getting 13 episodes and a Christmas special. Now? The number is coming down.

There are three likely reasons, although we’re clearly on the outside so don’t have the definitive answer as to why. But a few possibilities.

The first is good old fashioned cost-cutting. That Doctor Who is an expensive show to make, one of the most costly on Auntie’s budget. As such, the same number of boxsets will likely shift at the end of the series whether the BBC commissions ten episodes or 13.

Perhaps, though, there’s a decreasing confidence in the show from within the BBC. Whilst many ratings stories that were penned following series eight and nine of the show were quite basic, and failed to consider the likes of catch-up and the dramatic change in people’s viewing habits, the cold truth is that Doctor Who doesn’t shift as many lunchboxes as it once did in the UK. The BBC Worldwide merchandise machine was far less richly rewarded that it was in the David Tennant days, and the commercial reach of Who may be a little more limited than it was.

The worldwide audience certainly isn’t. As the audience in the UK has settled, so the show has continued to grow in support around the planet, so it’s still clearly a big deal to the BBC. But also, it’s a bit more of an unknown than it was. The casting of a new Doctor, be it Peter Capaldi, Jodie Whittaker or Matt Smith, always brings with it an element of risk. And that’s compounded by the wholesale changes behind the scenes, too. New showrunner Chris Chibnall will be putting his own stamp on Doctor Who, and there’s a sense that the show is heading a little into the unknown. A good thing, certainly, but a risky one.

The other option, of course, is that Chris Chibnall himself requested the format change. That he asked for slightly longer episodes, and fewer of them. It’s understood that he’s making lots of changes behind the scenes of Doctor Who, and maybe that’s one of them that he’s specifically sought. Furthermore, there’s the argument too that the old TV drama staples of 13 or 22 episodes have been challenged, and lots of series are seeing their episode counts come down around the world.

But as a fan at the end of all of this, it does feel like the depreciation in the amount of Who that we get – longer gaps between seasons, fewer episodes, the old spectre of split seasons – betray some change of confidence in the show itself. Given what strong form it’s been on, were that to be the case, it’d be a real disappointment.

Doctor Who series 11 starts in autumn 2018.