Announced late in 2012, Kingsman: The Secret Service is an action adventure comedy loosely based on a spy comic book written by Mark Millar and illustrated by Dave Gibbons. The film's director, Matthew Vaughn, achieved considerable commercial and critical success in 2010 with his version of another comic book written by Millar: Kick-Ass.

The film follows Gary 'Eggsy' Unwin, an unrefined but promising street kid. Eggsy is recruited into an ultra-competitive training program for the secret Kingsman agency, just as a global threat emerges from a twisted tech genius.

In May and then July 2014 the film's distributor, Fox, submitted two trailers for Kingsman: The Secret Service with a 12A request. These trailers contained some explosions and the sight of guns and other weapons, but there was no clear detail of blows making contact and no bloody injury detail, and so the BBFC passed them at 12A. Different versions of trailers were later age rated at both 12A and 15.

The distributor then sought advice from the BBFC, stating that they would like to release the work at the 15 category. In September 2014 they submitted an unfinished version of the film for an advice viewing, with the end credits missing, a temporary musical score, and a number of scenes without completed special effects. BBFC staff viewed the film and highlighted one particular sequence, the 'church massacre', which contained a strong, cumulative focus on blood and injury. However, they also noted that as the violence was stylised and highly cartoonish, and the action fast-paced and rapidly edited, it was likely that the scene would only need small adjustments to fit the 15 category criteria in the BBFC Classification Guidelines. The BBFC also advised caution over some of the unfinished special effects elsewhere in the film, specifically scenes of heads exploding.  

The distributor requested that the BBFC Compliance Managers (previously called Senior Examiners) meet with the filmmakers to talk through some of the film's key sequences. Discussions focused on whether it was possible to tone down some of the stronger moments of gory detail and violence, especially in the church scene, a scene shot in a single take. To achieve a 15 the filmmakers decided to reduce blood and gore effects where possible. They also explained the exploding head effects would be highly unrealistic.

The distributor submitted a second, still uncompleted version for another advice viewing some weeks later, having made some changes. The bloody detail of the completed special effects – including the exploding heads – now appeared even more unreal and cartoonish, and the violence in the church scene seemed less impactful than previously, following minor adjustments that included the finalised music soundtrack. These elements all served to emphasise the deliberately over-the-top nature of the violence, and so the BBFC advised the company that a 15 classification was likely.

Kingsman: The Secret Service was formally age rated at 15 in November 2014, ready for an early 2015 release. The short classification information, BBFCinsight read 'strong bloody violence, strong language'. The more detailed insight notes that there are:

'…a number of highly stylised choreographed fight scenes that are distanced from more brutal and realistic portrayals of violence. The fighting involves the use of weapons such as guns, knives, axes, explosive devices and prosthetic legs fashioned as razor-sharp blades. The action in these scenes is fast-paced and rapidly-edited, and although the violence is strong and bloody there is no lingering focus on pain and injury. Bloody injury detail is also present in the aftermath of violent incidents but this is again not dwelt upon to any undue extent.'

The film also contains several uses of strong language ('f**k' and 'motherf**ker'), together with other, milder terms, such as 'dickhead', 'wanker' and 'prick' – plus occasional discriminatory language such as 'nigger' and 'fag'.

There are also some strong sex references, with a character making a masturbation gesture and talking about 'secret sauce' and the protagonist's evil stepdad implying that his mother might be interested in a threesome while he's away.

Released on 29 January 2015, Kingsman: The Secret Service opened in second place at the box office (behind Disney's Big Hero 6), and went on to earn over $404,000,000 at the international box office and a further $29,000,000 in DVD sales – several times over the production budget.

Kingsman: The Secret Service was one of the films to generate the most feedback to the BBFC from members of the public during 2015. One of the issues raised was the level of violence in the film at 15, with many correspondents stating that they thought it should have been awarded an 18 category. Other complaints focused on a scene involving a crude sex reference in a comic context.