Countdown is a staple of tea time viewing and as it comes up to its 40th anniversary, fans could be forgiven for thinking it no longer holds any secrets.

But the ultimate test of mathematical and linguistic skill still has a few behind-the-scenes secrets it has yet to share. 

Despite the slick appearance of the Channel 4 show, former winner Gary Woodward has revealed what filming is really like. 

The Countdown star, who appeared on the show nine times, revealed the programme uses fake scenes to disguise rude answers and even has a special winners group  - although not just anyone can be a member. 

And according to the The Sun,, those aren't the only secrets the show is hiding.

While the show may appear to be a slick operation to viewers, the reality is a different story

Most may assume that contestants can't use swear words - but in fact they can, albeit with a reshooting twist.

While the show won't broadcast the original potty-mouthed answers, bosses still let contestants take home their points. 

Instead producers of the show simply swap out the rude word for a more appropriate one with the same number of letters. 

A former audience member, who wished to remain anonymous, told The Sun that one rude answer was so bad producers were forced to ban it from airing because of fears over complaints. 

They explained: 'There were a couple of retakes and the funniest one was when a guy said 'pisser' in the anagrams round.

'It was a great six-letter word but they couldn't use it. I think it's because they feared getting complaints.

'He still got the points but right at the end of filming they recorded him saying a more palatable six-letter word instead.'

Gary also revealed that the programme often has to re-record scenes if things go wrong.

He explained that the crew need everything to be perfect so if there's a mistake from the presenter, a slip-up, any unexpected laughter or sneezes, they have to re-shoot the scene.

And the Peterborough native revealed the easiest way to tell if scenes have been stitched together.

He told the publication that if the cameras cut back to a contestant while they're choosing a vowel it's because they've used a cover shot.

This means the producers can cover up any mistakes - including spelling out rude words.

Other secrets the quiz star revealed included a secret group just for winners of the show. 

The former contestant explained that for those who did well on Countdown, they were invited to an elite Facebook group.

But he added that not just anyone could join and membership is reserved for those who have won more than once. 

Gary also confessed the group is nerdy but like a big family and they all share memes and solve puzzles.

He said: 'It's like a big family, we share funny memes and do daily challenges as well as solving the tea time teasers together.

'The rule is: you can post your answer but you have to change it so that only the author of the post can see it, which avoids ruining it for other people.'

Gary also told the publication that to watch the show you have to be quick off the mark, because the producers overbook the audience. 

He confessed that he had seen people be turned away more that once after all the seats were booked up despite them thinking they had a ticket. 

And it's even harder to get a spot as a contestant.

Gary revealed that he applied to go on the show as a dare but even after sending in an application, it still took a long time for him to be invited back to audition. 

As with all great TV, where would a show be without a Christmas special. 

And Countdown is no exception and makes sure to get its ducks in a row well advance, often filming their festive episode at the end of summer. 

A source told the newspaper that they found the experience of filming for Christmas in September 'odd' because it was still sunny outside.