By Narbeh Minassian, news reporter
The time on your ticket is 7pm, but you already know it's not going to start then.
So, what time do you get to the cinema?
If you're arriving at 7.10pm, you're almost certainly safe, but any later and you may cut it fine.
Here, we've gathered information from the UK's major cinema chains and spoken to experts about how long you can expect adverts and trailers to run until the main event actually begins.
Cineworld
According to the Cineworld website, ads and trailers "normally last between 30-45 minutes before the actual film begins".
The cinema also asks customers to collect tickets at least 20 minutes before the listed time "to make the most of their visit".
Odeon
There appears to be a shorter wait at Odeon, which claims advert and trailer length is "typically 15-25 minutes" - but this varies with each performance and can be "considerably less".
"We always recommend to avoid disappointment you arrive with enough time to enter the screen at the scheduled performance start time," the website says.
Everyman
There's a wider range at Everyman, which says it plays 25 minutes' worth of adverts and trailers.
But beware - "the length of ads and trailers varies for special events and it can be between 15 and 40 minutes, subject to type of event".
Showcase
There isn't any specific information on the website and we got no response when we reached out to them, but Showcase did respond to a customer on social media on this very question.
In a May 2022 tweet, the cinema said: "The advertised time is when the adverts/ trailers start and are approximately 20-25 minutes long before each show."
Vue
Vue offers a more precise window: "Please be aware that most films have around 20 to 25 minutes of ads and trailers before the feature starts."
Its only recommendation is to be in your seat at the time stated so you "don't take any chances in missing the start of your film".
'In general, it's 24 minutes'
Karen Stacey, the chief executive of Digital Cinema Media, which supplies advertisement for the likes of Odeon, Vue and Cineworld, told Sky News the wait is typically 24 minutes - 12 minutes for ads, and 12 for trailers.
This remains true whatever the film and whatever the time of day, with about 95% of DCM's schedules "exactly the same".
"It's very formulaic, that's what consumers are used to," she said. "By making it consistent in length, people are always happy to come and join in."
She said 24 minutes gives schedulers enough time to prepare the film and allow a more staggered entry for the audience - while also bringing in revenue.
Any longer than half an hour, though, is "rare".
"Cinemas want to have as many films in as possible and they want to be mindful they don't finish too late in the evening," Ms Stacey said.
"My experience working with them is they are quite strict."
Are there rules over the length?
As the above suggests, there aren't any set rules or procedures governing cinema advertising length.
Kathryn Jacob, chief executive of cinema advertising company Pearl & Dean, said the length was determined by the cinema.
"Some cinemas take only one ad, like the BFI IMAX, and the maximum length is determined by the cinemas themselves," she told Sky News.
"Factors determining the length depend on demand from advertisers and the films that a cinema might want to showcase to the audience that's at the screening via trailers."
Cinema policy is the key decider and she said research has shown audiences find advertising in cinema "part of the entertainment".
Do viewers like the adverts and trailers?
Ms Jacob may have a point.
According to research published by DCM, advertising in cinemas is more effective than in any other media.
For a 60-second advert in the cinema, viewers will watch 48 seconds, which is a far higher proportion than TV or social media.
It is also highly trusted, with DCM citing a survey by IPA Touchpoints claiming nearly 100% of respondents say they trust what they see in the cinema - for comparison, 75% trust TV adverts.
Avid cinema-goer Bill Boswell, who pays £18 a month for an unlimited pass at Cineworld on the Isle of Wight, said he was happy to wait.
"I know that these adverts help pay for the cinema to run," he told Sky News. "The cinema is my place to escape, so it's good for my mental health and I would not want to lose it.
"If I watch at home, I can sometimes reach for my mobile phone, but a film on the big screen would get my 100% attention, so I just accept the pre-show adverts."
But what are the drawbacks?
The main thing Mr Boswell considers is his car, as his nearest Cineworld offers three hours of free parking.
"I would sometimes plan on 30 minutes of trailers and work back so I can fit the free parking in, as the cinema costs enough already," he said.
"If the film is more than two and a half hours, I park outside town and walk to the cinema."
Consumer expert Martin Lewis raised parking tickets as one of the issues in a 2019 tweet, in which he said he waited 33 minutes for a film to start.
Responding to one user, he said greater clarity would help customers to save on parking tickets and babysitting, while giving "legitimate expectation".
"And there's no rigorous research that prices [cinema tickets] would go up - they're often set by market demand," he added.
Are there alternatives?
If you want to avoid the pre-show altogether, your best bet might be independent or community cinemas.
Draycott Community Cinema, for example, is the only cinema in the Somerset village and is run by volunteers.
Committee member Chloe Haywood told Sky News they are always debating how long to make their pre-show.
They try to keep it to two short trailers, often without any adverts - though they are planning to find a sponsor later this year.
"We do find that it sets the audience up for the screening," she said, referring to their brief pre-show.
"We don't have trailers for long. They're to advertise the next two films, any local news that might be of interest, and then standard 'switch off your phones' type info."
