10 Most Obvious Doctor Who Plot Twists Ever

Orphan 55 well and truly hammers home its ecological message in the final moments, which is reflective of the previous 45 minutes.

The Planet of the Apes-style twist at the end may as well have been lit up in big neon letters that read: IT'S REALLY EARTH! Chosen as one of the worst episodes of Doctor Who by readers of Doctor Who Magazine, the episode begins as a fairly standard base-under-siege story set inside an all-inclusive resort. But then it shifts, with the Doctor becoming hyper-focused on the identity of the planet itself, which is almost completely barren.

The way the script is constructed heavily signals to us that this is a planet that we know, and a lack of recognisable aliens means that it's not one known for its extra-terrestrial population.

There are frequent references to high levels of CO2 in the outside world, a "ruling elite" that gets to evacuate the planet, and then there's the references to "solar blistering." It all sounds very familiar and close to our own climate emergency.

We finally get the confirmation that it's Earth when the Doctor discovers the sign for Novosibirsk underground station. It's a direct callback to the Marble Arch sign from The Mysterious Planet, confirming what we'd all figured out about 20 minutes earlier.