Sarah tended to rebel against the third Doctor's condescending manner, but soon grew to like him as his attitude softened. She developed a better relationship with the Doctor after he regenerated into his fourth identity. During the regeneration (between Planet of the Spiders and Robot) Sarah's hair lengthened considerably making her appearance more feminine and even more attractive. She became less of a feminist and more a lady who was independent by nature with an insatiable thirst for facts.

Her feminist approach was no-doubt softened when Harry Sullivan joined them. He was assigned by the Brig to look after the new Doctor. But when he was whisked away to a beacon in space millions of years in the future he was way out of his depth; and in trying to help he continiously caused near-catastrophes. Ian Marter's portrayal of Harry made the character hugely sympathetic but he only stayed with the series for a year before leaving, later going on to write some of the many Doctor Who novelisations.

But when Elizabeth Sladen left it made front page news - something that normally happened only when a Doctor left. But after three years, Sarah was to fall out with the Doctor in the Tardis and go to pack her bags. The Doctor then received a summons from Gallifrey, and he wouldn't be allowed to take Sarah there, so he told her they really would have to part. She was devastated, but was returned home. She was last seen walking off whistling "Daddy wouldn't buy me a bow-wow!" It seemed unintentional enough, but a future producer was to decide it would be prolific. The Doctor was to send a present after her, a present she wouldn't discover for three more years ...

So the Doctor was alone for only the second time in the series, as the Tardis headed for the home planet of the Time Lords - where awaited the Deadly Assassin ...

"So what?" you might say; it wasn't the most memorable of stories. However, it remains the only televised example of the Doctor arriving on a planet without a companion, (until 1996); although he didn't remain companion-less for long, when the shapely form of Leela stormed into his life, in plunging leather costume and high boots! This thigh-flashing Sevateem warrior was going to ensure that no sixteen year old was going to grow out of Doctor Who!

But these costumes were practical for Leela. She was not unlike a female Tarzan; a savage, acting on instinct, hunting by smell and sound. Put her together with the Doctor and you have a situation not dissimilar to Pygmalion / My Fair Lady where Professor Higgins taught Eliza Doolittle "how to be a lady." Only here, it was the Doctor who was slowly introducing Leela to the wonders and refinements of the Universe. Such a situation could be both amusing (her ignorance of manners when she started eating the meat with her hands causing Professor Litefoot to do the same so as not to show up his guest) and suspenseful in her instincts - when Leela sensed danger she was invariably right.

It worked. The similarities with Star Wars were never mentioned because the robot dog was, if anything, better than his contemporary movie counterparts. Part of his success was the way in which he would correct the Doctor, deflating the Time Lords ego with a smug comment!

K9 mark one was built by Professor Marinus, and stayed with Leela when she left the Doctor's side to marry a Gallifreyan - quite something when their first sign of mutual interest was when they were soppily holding hands in the final episode of The Invasion of Time! "Is this Leela?" asked the incredulous viewers. No, it wasn't. It was the result of Graham Williams' dumbing-down of the programme. But at least when K9 went with her it gave Louise Jameson's character some dignity in leaving.

K9 mark two was built almost immediately by the Doctor. The only difference was this K9 was grey and could respond to ultra-sonic signals.

Perhaps helped by the developing relationship between Tom Baker and Lalla Ward, this Romana was much more successful, fitting into the required sidekick mould without losing her knowledgeable and aristocratic background. The more time she spent journeying with the Doctor, the less she wanted to return home. She had come to understand why the Doctor resented the Time Lord rule of non-interference, and how impractical it was when confronted by the evils of the universe. Indeed, not just this universe, but also another one called E-space, where she decided to remain. Maybe the fact that the Time Lords were demanding her return may have had something to do with her decision to stay in E-space where the Gallifreyans could never get her, and where she could do some good, as the Doctor had always done in the home universe.

Writing out K9 could have been difficult. Such was the uprising when it was suggested that K9 was to be dropped that killing off the robot dog was unthinkable. Besides, the Doctor could simply build another one. And there was no danger of K9 running off and marrying anyone (unless he came up with a metal bitch!) so in his last season he was seen to be vulnerable, and constantly needing to be repaired.

In Warriors Gate, while in this universe, K9 was damaged beyond repair. The only thing that could restore him was to pass through the mirrored gateway and remain in E-space - a one-way trip that could save his life. So K9 mark two stayed with Romana mark two; a gift through circumstance from the Doctor.

(It is worth noting here that K9 mark three was constructed by the Doctor and given this time to Sarah Jane Smith. She discovered her "bow-wow" in K9 and Company, the series' one and only spin-off.)