Alesha Dixon has recalled her shock after a stage invader crashed the BGT judges' desk in the live shows.
An 'unwanted guest' made an appearance in the live semi-finals earlier this week.
Towards the end of the second semi-final, one member of the audience decided to crash the judges' desk.
After illusionist group Magus Utopia performed, the random person ran up to the judges' panel and began to hit the buzzers before being taken away by security.
Host Dec was quick to say: "Apologies for our unwanted guest, some people just want to touch the buzzers."
Simon Cowell remarked: "It's going to be one of those nights."
A video shared on Twitter by @scubasteve1414 said: "What a take down! Take a bow mr security man #BGT #BGTSemiFinal"
Talking about the incident ahead of tonight's final, Alesha said: “I have to be honest, in the moment, that did really scare me."
She told the Daily Mirror newspaper: “I didn’t know what his intentions were and when I looked over to my left he was running over so fast that I pushed my stuff away from the desk and spun my chair around. I was literally ready to take off because I didn’t have a clue what he was doing.
“At the moment, everyone is quite sensitive and on edge and it was a joke gone too far."
Alesha added: “You can’t tell those jokes when people are a bit nervous at the moment about being in venues – he was an idiot and that was silly.
“In the moment it was quite scary because it was unpredictable and I didn’t know what he was going to do.”
Britain's Got Talent 2018 final airs Sunday, June 3 at 7:30PM.
The acts in the final are acrobats Giang Brothers and comedy singer Micky P Kerr, dancers DVJ, father and son singing duo Tim and Jack, comedian Robert White, singer Gruffydd Wyn Roberts, singer Donchez Dacres, singer Calum Courtney, comedian Lost Voice Guy and the D-Day Darlings in the final.
As well as the finalists' performance, the last live show of the series will also see some guest performances from The Cast Of Magic Mike from Las Vegas and the Cast Of Tina Turner The Musical