The Sarah Jane Adventures (BBC1, 4.35pm); The Car Scrap Trap: Tonight (ITV1, 8pm); Bill Bailey: Tinselworm (Channel 4, 10pm)

MANY remember Elisabeth Sladen when she first played intrepid journalist Sarah Jane Smith in Doctor Who back in the mid- Seventies, and those older fans will be tempted to tune in to this children’s scifi spin-off because it features retiring timelord David Tennant.

“When I heard the news that David was going to be joining us, I was absolutely over the moon,” says Sladen. “Not only has it made my day, but it will also make the viewers’ day.

“It’s fantastic news that Sarah Jane is going to spend some time working with The Doctor again, and is testament to just how successful this CBBC series is.”

The guest appearance was lined up by Russell T Davies, the executive producer of both Doctor Who and this hugely successful version for younger viewers.

“Viewers thought they may have to wait until November for the next full episode of Doctor Who, but this is an extra special treat,” says Davies.

“And it’s not just a cameo from David – this is a full-on appearance for The Doctor as he and Sarah Jane face their biggest threat ever.”

Those are strong words indeed when you consider the fact the pair have dealt with some terrifying foes over the years.

Sarah Jane’s first appearance – on December 15, 1973 – was in the first episode of the four-part adventure The Time Warrior.

A fearless journalist after a good story, she ended up being transported to the Middle Ages, where she and the Doctor (then played by Jon Pertwee) met a Sontaran for the first time.

Although Sarah Jane was initially suspicious of The Doctor, the pair soon became firm friends, and she became his permanent travelling companion.

She even nursed him as he changed from Pertwee to Tom Baker in 1974, before he returned to her old life two years later.

But Sarah Jane’s popularity meant that Sladen was invited back. In 1981 she appeared in K-9 and Company, a pilot for a planned series that wasn’t commissioned, and the 25th anniversary show The Five Doctors. She reprised the role for other spin-offs and audio adventures, before making a triumphant return to the programme in the 2006 adventure School Reunion.

She hasn’t looked back since, with The Sarah Jane Adventures proving hugely popular with children and adults alike.

Her latest two-part story began yesterday, with the reporter finally looking to settle down with charming Peter Dalton (guest star Nigel Havers). However, her big day could be ruined as The Doctor arrives – and the two old friends must work together to save the Earth from an alien threat.

YOU take your old banger to be scrapped and get £2,000 off the price of a new, greener model. It sounds like a winning situation for everyone, right?

Well, as this latest edition of the news magazine series Tonight reveals, it might not be such a good deal after all.

The Government has invested hundreds of millions of pounds in subsidies for new car sales, and the scheme has been heralded a success.

However, Morland Sanders sets out to investigate whether it really is so beneficial for the consumer and taxpayer.

Many independent dealers say that shopping around for a new car can often result in a saving greater than the £2,000 scrappage subsidy. And with many car manufacturers raising their prices, many feel taxpayers’ money is being wasted.

BILL BAILEY, the funniest bearded, babbling, bug-eyed druid the world has ever seen, returns to the stage with a truly spectacular set, making full use of his prodigious musical and comedic talents to bring down the house at Wembley Arena.

Filmed at the end of his sellout 2007 tour, the show includes Bill’s trademark musical inventiveness and verbal brilliance, plus films and animation by award-winning film-maker Joe Magee.

If you’ve only ever seen him as a guest on TV panel shows, you’ve only enjoyed a glimpse of the true brilliance of a man who once described himself as part-troll.