John Sergeant hauls his partner Kristina Rihanoff around in series six of Strictly Come DancingPhoto: PA

Strictly Come Dancing has returned for a seventh series. We take a look at the sequinned, cha-cha-chaing phenomenon, from its first series in 2004 up to the present day.

Strictly is the world's most successful reality TV format, according to the Guinness Book of World Records. The BBC has sold the show to 38 countries around the world.

Each of the women’s costumes are worth around £2,000, and are specially made by a team of 10 costume-makers.

The contestants’ hair is done by Lisa Armstrong – or Mrs Anthony McPartlin, as Ant and Dec fans will know her.

In the six series so far, the winning couples have been: Natasha Kaplinsky and Brendan Cole; Jill Halfpenny and Darren Bennett; Darren Gough and Lilia Kopyova; Mark Ramprakash and Karen Hardy; Alesha Dixon and Matthew Cutler; and Tom Chambers and Camilla Dallerup.

As well as the six series, there have been five Christmas Specials.

The judging panel consists of Bruno Tonioli, Alesha Dixon, Len Goodman and Craig Revel Horwood. Former winner Dixon has replaced Arlene Phillips, who left amid rumours of ageism at the BBC.

Phillips has now moved to The One Show, where she will be the resident Strictly Come Dancing expert.

Darcey Bussell, the former ballet star, will also join the panel for the final three shows.

A voting fiasco in the last series – in which the phone lines were cut off half-way through a vote when it was spotted the public would not be able to affect the result – has moved the BBC to bring in some statistical backup. Consultancy firm KPMG have worked on the system to make sure that any couple can be saved by popular vote.

Allegedly, the letters on the autocue that Bruce Forsyth reads from are so huge the audience has to be asked not to mouth along with him as it scrolls.

This year, for the first time, there will be Friday and Saturday shows for the first two weeks, and couples will perform on both nights. The judges’ scores will be combined on Saturday before the public vote.

Len Goodman gets more fan mail than anyone else on the show.

Fellow judge Bruno Tonioli was fined last year for breaking no-smoking regulations when he tried to sneak a crafty cigarette between dances.

The lowest score ever given by judges was eight out of 40, bestowed upon Quentin Willson and Hazel Newberry for the cha-cha-cha on 23 October 2004.

The next worst were 10/40 (Fiona Phillips and Brendan Cole) and 12/40 (three times - Diarmuid Gavin and Nicole Cutler; Diarmuid Gavin and Nicole Cutler again; and John Sergeant and Kristina Rihanoff).

A perfect 40/40 has been awarded eight times in the main series, with Lisa Snowdon and Brendan Cole pulling off the feat three times in series six alone. It has also been given four times in the Christmas special.

The 2008 final attracted 13 million viewers, beating the 2006 and 2007 finals’ totals of 12 million.

This year, former boxer Joe Calzaghe is the bookmakers' favourite to win at 9/2. Jo Wood, the estranged wife of Rolling Stone Ronnie Wood, is the longest-priced at 25/1.

Former England cricketer Phil Tufnell is tipped to be this year’s John Sergeant – i.e. cloven-hoofed comic relief.

The Duchess of York, Richard Madeley and Sharon Osbourne all turned down offers to appear in this year’s show.

Since the last series, presenter Tess Daly has given birth to daughter Amber Isabella in May. She now has two children with her husband, fellow TV presenter Vernon Kay.

Strictly dancer Brendan Cole has himself been a ‘celebrity’ on reality TV, having been a runner-up on ITV’s Love Island in 2006.

In series six, contestant John Sergeant withdrew from the show, declaring that he was worried that he might win it. Sergeant had been called a "dancing pig" by one of the judges.
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