Onlookers were concerned when they saw him in the early hours of the morning in a parking lot in south-east London.
Four police officers spoke to him before his family came to take him home.
The footage shows the reality TV star, clad in a blue and white jacket, looking puzzled as he is detained by police.
He had been seen in the parking lot behind a row of semi-detached houses five miles from his family’s home in Kent.
A resident of Bexleyheath said: “I don’t know why he was there.
“I didn’t realize who it was until I went to Google. “
Last Sunday’s incident – 30 yards from a police station – came days before it was revealed that Fincham, 30, had separated from Towie’s girlfriend, Frankie Sims, 26 .
Jack’s reps declined to comment. A source said: “I’m sure if Jack wants to use social media and explain the situation, he will. “
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Nine days earlier he had posted pictures of himself on vacation in Ibiza. On Friday, he uploaded one in the sun with the caption: “Think about things. “
News of her split from Frankie came just hours after her ex Dani Dyer, 24, dumped her crook boyfriend Sammy Kimmence, who was jailed for defrauding two retirees.
A former stationery sales manager, Jack rose to fame in 2018 after he and Dani were crowned Love Island winners.
The pair shared the £ 50,000 prize and continued dating, moving in together and starring in their own spin-off.
But in 2019, Jack was forced to apologize publicly after it was revealed he had had a cocaine binge. He admitted that he “feared” to confront Dani’s father, Danny Dyer.
He became a dad with “great friend” Casey Ranger in January 2020.
Last November he was injured in a car crash outside a pub in Dartford which saw his £ 35,000 Mercedes canceled.
The Met said: “Police were called at 5:18 am to report that a man was acting suspiciously. Officers attended and detained a man. No offense had been committed. He was picked up by his family.