It's finally happened; T-Shirt has broken free from the evil clutches of T-Bag. Now he's leading a normal life as a teenager in a small suburban town, and he's got a nice little earner on the go - "Tommy's" - a teashop-cum-cafe. It's a guaranteed money spinner for T-Shirt, the best tea maker in the land.

The place is such a success that T-Shirt advertises for staff. Enter a straggly old bag lady pushing a supermarket trolley seeking work.

It's some time before he recognises her. Can this sad, pathetic creature really be T-Bag, the one-time omnipowerful high priestess of the T-Set? It's true. Down on her uppers, T-Bag sees the fateful encounter as her one last chance to seize her former glory. T-Shirt alone knows the teamaking secrets that can restore her magical powers. So it is that she worms her way into T-Shirt's employ and in no time at all, has him wrapped around her little finger.

Her megalomania knows no bounds. She forces T-Shirt to build her a time machine so that she can seek out a batch of the now extinct magical tealeaves. But the best laid plans...

In search of her goal, T-Bag launches the whole of "Tommy's" into space. No longer doomed to the provincial back-waters, the cafe-cum-spaceship whisks the duo off, destined for a weird and wonderful journey through history. This wild ten part adventure story features the return of Liz Estensen who created the role of T-Bag so successfully in the first five series.

It was Lee's idea to set the drama inside an alphabet-based board game; each letter would suggest a character and a story ... for instance, T-Bag would be the main character on the T-Square. A little girl would become the main protagonist who must work her way round the board, overcoming obstacles of every sort but finally winning the game and emerging triumphant.

Our very first pass at the idea was incredibly grandiose, involving all sorts of impossible special effects and fantastic landscapes. Draft One was greeted with a resounding scowl, and a new objective was added to the original remit: keep it cheap, lads. So, thinking inexpensive, Lee and I began again. And again. And again. By now, the pressure of time was impacting on everyone, so the hard-pressed director made it plain to us exactly what he reckoned he could and couldn't achieve, given the time and the budget, and pretty much dictated half of Episode One to us! Overnight we had gone from being screenwriters to shorthand typists! As relative newcomers to television, we had no real say at this stage, and we found our (admittedly over-enthusiastic) efforts on Series One to be massively and disappointingly diminished.

There was one mad final rewrite at an even later stage when one of the producers had the idea of peppering the character dialogue with alliterations appropriate to the "square" on which they appeared. Cue: several singularly unsayable sentences. We were never at home with this, finding it stultifying, strained and stonking-well stilted. Still, there were things about Series One which worked really well. We were especially heartened by the rapport which quickly developed between Elizabeth Estensen and John Hasler as T-Bag and T-Shirt. Lee and I became much more interested in their growing relationship than in almost anything else, and I think we realised pretty early on that we'd stumbled upon a terrific double-act in the making. The T-Room scenes, for me, became the highlights.

We were also stuck with a title we loathed: "Wonders In Letterland". We were quietly pleased when, thanks to a copyright infringement on somebody's part, the show was subsequently renamed: "Troubles With T-Bag". This wasn't perfect either, but at least it focused attention on the central character rather than on the board game, suggesting the possibility of further, newer adventures in different settings. T-Bag would, from now on, feature in the title of every one of the nine series and the four Christmas specials (not to mention the book and the CD of songs from the series. Okay, I lied about the CD).

Episode One of Series One is the only show in which T-Shirt doesn't appear: as a result, T-Bag comes across as a slightly off-the-shelf-ish "wicked person" made individual more by Elizabeth Estensen's flamboyant performance than by any particular character delineations in the script. But as soon as we arrive in the T-Room, in Episode Two, the fun starts. A fractious mother-and-son relationship kicks in. The famous headaches appear. The sparring and joshing and backbiting begin. Soon we realised that we had created, almost by accident, that strangest and most delicious of items: baddies who we like even better than the goodies!

T-Shirt's ambivalent role in the relationship became the key; T-Bag's frustrated dependency on the boy to make her vital cuppas, along with her ever-growing megalomania and stupidity, powered the partnership for year after year. Today I'm amazed that all of this was so firmly established right from Series One, when Lee and I were still feeling our way as writers.

I don't think Lee would disagree with me when I say that much of the credit actually goes to Liz and John for so subtly fleshing out their roles: time and again, on studio days, I'd stand behind the cameras and wriggle my toes in delight at the way they interpreted scenes which we obviously hoped were amusing but which then came out hilarious. Where would we have been without Liz and John? Answer: standing behind the cameras filming a sofa.

So as you can see, the making of a series took about five months from start to finish, with most of the writing happening pretty intensely in the first half of that period. (And just in case all of that wasn't head-mincing enough, Lee and I were simultaneously conceiving and writing Series Two of our other show, "SPATZ"!) So there you have it. The Train Spotter's Guide To Series 7. Well, you did ask!!

A well-known producer recently put it to me perfectly: "Us producers (metaphorically speaking) always want our writers to give us Mickey Mouse - nice, smiley, a bit bland, yet universally (inexplicably!) popular. But writers keep giving us Donald Duck! - all that angry quacking and storming about, muttering under his beak! - treading on garden rakes and knocking his face inside out! We would really rather they gave us THE MOUSE!" It's a sentiment which explains why so much television is the way it is.

One of the hardest things to deal with when writing for the screen is that, actually, there exist two versions of your script: the one which explodes inside your head, full of beautifully-timed comedy sequences, shot with pace and panache on a multi-million dollar budget; the other version is the one which turns up one day on the telly. Often the difference between the two is astounding, the result disappointment. Lee and I often bemoaned the way T-Bag always seemed a mere shadow of what it could have been. And yet ...

The years roll by, and the versions which once rattled around in the addled nut have dissolved away. All that remains is the show as it finally hit the airwaves. It's a lot easier to be objective about it a decade on: any time I sneak a look at T-Bag these days, I do find there's a massive amount to enjoy; some of it I'm very proud of - usually scenes and sequences where everything came together tremendously well. Donald Duck moments. There's often some terrific comic acting from our fantastically talented cast of guest performers - mixed occasionally with turns so dud you're laughing even harder for different reasons ... and I can absolutely see why it ran for an incredible 94 episodes. So the answer to your question: was I pleased with the finished series? is: "Not exactly, but I am now!"

Controversy rages amongst my family and friends: who was the best T-Bag? Tallulah or Tabatha? Liz or Georgina? I don't think it's possible to compare them. I love them both in very different ways. Liz's Tallulah is full of nuance and subtlely; she's petulant and vulnerable and pompous and a hundred other wondrous things which go to make the character incredibly human and endearing. It's a marvellous, sophisticated, funny and intelligent performance. Georgina's Tabatha makes me think of some hilariously insane cross between Harpo Marx and a Dalek. A completely unique actress, Georgina Hale brought unpredictability to the role - and to the series - which in my opinion is a very rare thing. That full-on bolshie bluster, the towering, rampaging stupidity, the sheer high-flying fearlessness of it all ... Tabatha may indeed be an acquired taste, but she is the T-Bag who makes me laugh the loudest, the longest and the hardest. So in the end, I'm incredibly glad that we ended up with two T-Bags. And had there been a third? Intriguing! Casting suggestions by e-mail, please ...