I recently reviewed the Doctor Who DVD release of ‘Planet Of The Spiders’ for CultBox.

I didn’t have a great deal to say about the story that was complimentary, but one of the few bright things that shone through the padding and the cosiness was the performance of Elisabeth Sladen as Sarah-Jane Smith.

In only her fifth story, Lis had already nailed the part of Sarah perfectly: the humour and the feistiness and the if-you-stupid-men-won’t-do-it-then-I-will attitude that were to become hallmarks of Sarah, the best companion the Doctor ever had, for the next thirty seven years.

Lis was more than just Sarah-Jane Smith, but her connection with Doctor Who came to define her career. She was a fan of the show long after she left the TARDIS on a street that the Doctor was convinced was in Croydon, a fiercely proud custodian when it was – to many people – a dimly-remembered joke, languishing in a forgotten attic at Television Centre.

Lis defended the programme to the hilt and in 2006 was rewarded for her staunch loyalty with a starring role in Toby Whithouse’s ‘School Reunion’ episode. Doctor Who had changed a great deal since her departure in 1976, but the essential tenements were still intact.

In fact, an older, more reflective Sarah-Jane – heartbroken and lonely in the long years since that day on a street that turned out to be in Aberdeen – was arguably Lis’s finest performance. The humour, the energy and the insatiable curiosity were still there, but there was a maturity and a sadness that demonstrated Lis’s often overlooked depth as an actress.

By the end of the episode, a new generation of children had fallen in love with Sarah-Jane Smith and within months CBBC’s The Sarah-Jane Adventures had been commissioned. K-9’s series in the eighties was a flop; Rose Tyler’s spin-off was never even made; yet Sarah-Jane’s has run for four successful series, with several episodes of Series 5 already in the can at the time of Lis’s tragic death.

This astonishing character was aptly described as the Doctor’s best friend, yet from 1973 to 2011 she had a million best friends, with every viewer who fell in love with Sarah also falling in love with the wonderful actress who portrayed her. Nothing is eternal, they say, but as long as Sarah-Jane Smith exists in our hearts, we will never forget Elisabeth Sladen, the person who gave her immortality.

‘A tear, Sarah-Jane?’ Yes; too many to count, in fact. Today, it really feels like the universe is united in sadness.