People can't get over insane age gap between Keira Knightley and Thomas Brodie-Sangster in Love Actually

When it comes round to Christmas time there is always a heated debate about what the best festive films of all time are.

Despite Home Alone star Macaulay Culkin coming out swinging this year, saying Die Hard doesn’t count, many in the UK wouldn’t even consider this to be the top contender.

The most beloved Christmas film for most Brits, and a lot of people in the United States too, is Love Actually.

The Richard Curtis Christmas-set romance film features an absolutely star-studded cast, featuring a few names that appeared in the movie before they were famous.

This includes Keira Knightley, who appears in a storyline in the film alongside Chiwetel Ejiofor and Andrew Lincoln, as well as a young Thomas Brodie-Sangster, who stars in one of the sweetest plots from the film alongside Liam Neeson.

One of Keira Knightley's breakout roles was in Love Actually (Universal Pictures)

The movie follows eight different couples, all of whom encounter love in different ways in the lead-up to Christmas.

Keira Knightley’s character Juliet is married to Ejiofor’s Peter, but in the most iconic scene from the film, Lincoln’s Mark confesses his love to her.

Brodie-Sangster’s Sam meanwhile falls in love with his classmate at school, all the while his step-dad Daniel, played by Neeson, is trying to connect with Sam after the death of his wife.

Now, based on those two storylines, you’d obviously think that Brodie Sangster must have been a young child and that Knightley would have been a full-blown adult, considering Juliet was getting married to a character played by a 26-year-old.

Well, many will be surprised to hear that the two of them are only five years apart in age, a fact that blows the minds of fans every year who watch the Christmas classic.

Keira Knightley was just 17 at the time of filming, whilst Brodie Sangster was 12, something made even more shocking by a side-by-side picture of the two.

One fan posted this detail to Reddit, with one viral comment quite simply summing up fan reaction, saying: “Hey what the f*ck?”

Others were quick to point out that this was pretty straightforward, considering 17 and 12 is about as big a five year gap in puberty as you can get, but one fan made a startling realisation about why this was actually significant.

They said: “She was closer in age to him than both the actor playing her husband and Rick Grimes holding the sign.”

The plotline involving Juliet being pursued by Mark, despite her being engaged to his best friend Peter, in secret is one that takes on a far creepier tone when you realise the age difference between them.

Whilst Knightley was 17, Ejiofor was 26 at the time of filming, and Lincoln was 30.

Speaking about the famous cue card scene in an interview with TooFab, she said: “I mean, there was a creep factor at the time, right? Also, I knew I was 17.

“It only seems like a few years ago that everybody else realized I was 17.”

Richard Curtis has stated in a previous interview with LADbible that it ‘didn't seem too peculiar’ at the time, but added: “I'm really interested in whether or not I would think ‘don't do that’ now.

"And that actually now we probably wouldn't have gotten someone as young as Kiera was in.

"The great thing now is that everybody is bold enough to say anything they don't particularly like in what you do - kind of gives you a filter these days.”