"Britain's Got Talent" fourth semi-final started off with a joke, in light of last night's mishap of a misplaced producer. The rest of the night went on without a hitch, despite the chaos brought to the Hammersmith Apollo by one act. Last night showed one of the weirdest of the 'BGT' semi-finalists this year and it was a different kind of show to Wednesday night's [VIDEO] highly talented performers.

"Britain's Got Talent" is so different at times that theTelegraph said it had "Too much wackiness, not enough talent."

This is the second to last semi-final of the series, only adding to the pressure to get through to the finals.

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However, Dec reminded viewers that there is also a wildcard place that will be given to one of the semi-finalists who failed to win a place during the live shows.

Variety acts wow audience

The night kicked off with noisemaker Olena Uutai who wanted to bring the sounds of her country to the 'BGT' stage.

Her non-traditional act did not impress the judges like her audition. David Walliams responded with, "I'm not quite sure what we were on when we put you through." The judges were unanimous in their dislike but praised Olena for the cultural aspect of her act.

Next was young opera singer Amy Marie Borg. Initially giving herself a 9/10 rating for nerves in her audition, she managed to put those nerves aside and made it through to the live shows. Last night, as Dec told her, she "Absolutely smashed it," and left the stage with a smile on her face.

Swansea Valley funny man Noel James performed third last night and had the audience on his side from the moment he stepped onto the stage. He used both jokes and impressions that included a frog and Robert De Niro, that even had Simon Cowell laughing, along with the other three judges.

Baba Yega an alien dance group gave an out-of-this-world performance, with straight faces and special effects. The act ended with them each shooting a confetti cannon into the audience, before raising their hands to their head to give a signal. The comments from the judges were mixed, despite the chaotic actions of the group afterward.

Father and son act, Jack and Tim, took their guitars to the stage once more with another original song. They made it to the semi-finals via Simon's golden buzzer when at their audition, they wowed judges with their chemistry and song-writing skills. Last night they received positive comments once again from all four judges.

Daredevil acrobat Sascha Williams impressed an audience who were both amazed, and fearful of his act. His circus background makes him no stranger to performing, but Sascha took his act to a new level for the 'BGT' semi-finals, adding fire and guitar-playing to his act. The judges were wowed by his dangerous act, and even more impressed with his talent and fearlessness.

Marty Putz calls himself "An inventor comedian," and for his semi-final performance he brought along some new inventions. Shortly before turning the entire theatre into chaos he received a buzzer from Simon and Alesha, and by the end of his act, he had received four, the first full house of the semi-finals. As David described it, the act was "Mayhem," the perfect word to sum up Marty's cartoonish act.

The show was ended with street dance group DVJ, also known as Diversity Junior. The group was taught by Ashley Banjo, alongside Nathan and Perry, who were all part of the dance group Diversity, who won 'BGT' [VIDEO] in 2009. The group performed to the same high standard and energy level as their predecessors, while also making it their own. The judge's positive comments could barely be heard over the cheers and excitement from the crowd.

Fourth pair of semi-finalists

The final three acts of the night were; DVJ, Jack and Tim, and Noel James. The first act of the night to go through via public vote was DVJ. The decision on the next finalist would be left to the judges' decision. If, like the previous two nights [VIDEO], the judges failed to make a decision, then it would go to a second public vote.

A unanimous judge's decision of three against one, put Jack and Tim through to the 2018 'BGT' finals, leaving only two spaces left to be filled on Friday night. Third-placed Noel James thanked the judges and audience for the praise he had been given on the show. When it was time for Dec to speak to the finalists Jack told him "This is my best audience ever," through his tears of happiness.

Jack and Tim are the third golden buzzer act to join the finalists. They take their place alongside David's golden buzzer and Amanda's golden buzzer for Gruffydd Wyn. The golden buzzer choices of Alesha Dixon and Ant and Dec failed to make it through to the finals.