Over the years, the Doctor has had many companions. They come into his world and live the unbelievable life until it becomes too much and they wish to live a simple life again.

While they’ve all come and gone, none have stayed with the Doctor through all of his incarnations. But what of Brigadier Alistair Gordon Lethbridge-Stewart, who, while not meeting every iteration of the Doctor, has met the most (alongside Clara Oswald) and made a significant impact on them all?

Before we get into the man, the myth, the legend, let’s take a quick look at the man who made the Brigadier possible.

Nicholas Courtney has perhaps the most impressive Doctor Who track record of all the actors involved with the show. He started his Doctor Who career as the hard-nosed Space Security Agent Bret Vyon acting opposite the First Doctor, William Hartnell in The Daleks’ Master Plan. It was this powerful performance that led the production team to consider him for the role of the Brigadier during the Second Doctor’s era with Patrick Troughton.

With two Doctors under his belt already, it seemed obvious that he was the right man to command the UNIT troops during the Third Doctor’s era.

The shape of Doctor Who would be forever changed by the presence of Nicholas Courtney. When Jon Pertwee’s tenure as the Doctor came to a close, so too did the regular role of UNIT and the Brigadier. But this would not be the end of such a talented actor’s stint within the show.

Few characters can claim the success of the Brigadier. Throughout the show’s initial 26-year run, Nicholas Courtney would reprise his role of the Brigadier and act along side every actor to play the Doctor save one, Colin Baker. That aside, however, he was even able to catch up with Paul McGann’s Eighth Doctor to record an audio adventure for Big Finish (and the Sixth Doctor for the audio company too). Surely the Brigadier is a force to be reckoned with.

Here we have a man who has stuck by the Doctor’s side since their first meeting, and yet he is not typically considered a companion. For most of the Third Doctor’s era, the Brigadier and the Doctor were inseparable, often playing “devil’s advocate” to each other’s ideas. They seemed to be best friends.

The Brigadier can almost be called the other side of the Doctor’s coin. While not a total opposite in every way, he is willing to do whatever it takes to save the day – even if this means wiping out an entire species.

But is this kind of attitude wrong? I guess that depends on an individual’s feelings. The Doctor has knowledge of things we can only dream of, and it would seem that he is also more optimistic than us mere humans. So the Brigadier’s cavalier attitude towards the alien threats that have invaded our world may more reflect our own views.

That said, he is also a military man, and as cliche would have it, he is more likely to blow things up than to talk to them. This sort of attitude would infuriate the Doctor and often times leave the two of them bickering to such an extent that would normally lead to the splitting up of the Doctor/Companion relationship.

We saw what happened when Adam Mitchell made the Doctor mad in The Long Game (2005): he was taken home and left in a bad situation, never to return to an ordinary (or even fully extraordinary) life. This sort of thing never happened to the Brigadier; in fact, he and the Doctor would often be seen dining together soon after the offending situations and arguments. The two would continue an on-again-off-again relationship until the Third Doctor needed to regenerate, but even then this did not stop them from continuing their friendship. It only put a stop to their everyday adventures.

The Doctor would return again and again to help the Brigadier whenever he was called to do so. He even left behind a means of communicating with him, something he has never done for any other companion – not even his own granddaughter.

After their split, the Brigadier would pop back into the Doctor’s life on many occasions, eventually meeting ever incarnation from Doctor number one to Doctor number eight (if you count the Big Finish plays). Even when the Brigadier made a judgment call ending in the extermination of another species to save the Earth, the Doctor was still willing to sacrifice his own life to save the Brigadier, as can be seen by the emotional Seventh Doctor’s comment while cradling what he thought was the Brigadiers lifeless body. This is something he would normally do for either the entire planet or for a companion.

According to the Unofficial Companion Rule, to join the ranks of a companion, you have to travel from one story to the next via the TARDIS. The Brig has never done this, yet he is treated in much the same way as the rest of the Doctor’s companions. Some have called him an associate of the Doctor, but I feel this does not describe their relationship properly. While he may not fit all the criteria of a full-fledged companion, he seems to have one-upped them all by becoming the Doctor’s friend.

Sarah Jane Smith could be said to fall into this category too, as the Doctor stopped by her place some time after parting ways with her and left her a gift – something we have never seen him do before, again not even for his own granddaughter. She even was said to be his “best friend”, but she wasn’t give a means to continually keep in contact with the Doctor.

Brigadier Alistair Gordon Lethbridge-Stewart has done what no other in the Doctor Who’s history seemed able to do. He befriended a man with no ties to anywhere, kept in contact with him almost till the day he died (as is evident from The Wedding of River Song), and all of this without spending any length of time in the TARDIS or telling the Doctor how brilliant he is.