This episode begins with David Tennant as a science teacher. He writes physics on the board and then struts around muttering a little bit. I absolutely detested science at school because they managed to make it as hideous as possible despite potentially being one of the most fascinating subjects. However, if I had a science teacher like DT, things could have been a lot different!

Despite a story about facing off bad guys at school, this episode is really based in finding out more about our new Doctor, and what happens to the people he leaves behind.

“He was a very uncommon man.”

The return of Sarah Jane was an emotional moment, but it came in two stages. First we saw the Doctor talking to her fondly, whilst she didn’t know who he was. She perhaps had her suspicions, but it was such a far-fetched idea from her point of view, she brushed it aside. We got to see the Doctor’s eyes fill with tears as he saw that she had carried on quite successfully without him and, more importantly, had not been put off investigating strange occurrences.

When Sarah Jane realised who he was, we had the second half of the reunion, which came under more strained circumstances. In the midst of an investigation at the school, she stumbled across the TARDIS and its owner and the memories came flooding back.

What was really interesting, though, was the conversation in the café, where she confronted him over why he had left her. His reasons to her weren’t so convincing, but later to Rose he confided in the troubles that his immortal status gives - all very Highlander if you think about it.

“The missus and the ex, welcome to every man’s worst nightmare.”

There are plenty of complex emotions all round, really. Rose was instantly jealous of Sarah Jane - almost the second she set eyes on her. Did she have a feeling that SJ was a former companion, or is she just unhappy with any member of the female species? We know she is protective of her relationship with the Doctor, and is particularly unhappy when Mickey asks for a place on the TARDIS at the end of the episode, but jealousy is a very unattractive emotion.

Meanwhile, as Rose and SJ giggle about life with the Doctor, it becomes clear to the older companion that her time with him is definitely been in the past.

“We are in a car!”

In the Sarah Jane Adventures, I found K9 to be a bit annoying, but in this limited dose, he is quite cute. I particularly enjoyed the connection Mickey made with the robot dog, and the moment he realised he was playing that role in the gang.

It was also interesting when the Doctor couldn’t decide what to call his “team”. Perhaps that is why he tends to travel with just one person, because too many requires a better name!

“If I don’t like it, then it will stop.”

The story that all this emotional stuff hangs on is the Krillitanes and their domination of a school in the hopes of world domination. The fabulous Anthony Head prowls around with greased back hair and offers the Doctor a particular glimpse of how life could be if he joined them.

You can easily see the bitterness inside the Doctor, the torment and the loneliness, despite being surrounded by companions both former and current. His ancestors were peaceful to a fault but this Doctor has barely controlled rage. However, when offered the chance to “become a God” he isn’t really swayed in the slightest and we know that our Doctor will be alright, despite everything he has been through.

As an aside, the CG wasn’t that great in this episode but it particularly went downhill when the creatures went outside. The shots of Anthony Head and a Krillitane on the rooftop were particularly dire.