Mohamed Abrini, who has been described as the "man in the hat" airport bomber after his image was caught on CCTV at Brussels airport, had spent about a week in Britain in July 2015.
According to 'The Sunday Times', 31-year-old Belgian of Moroccan origin came to Britain to look for potential targets for a "vast" jihadist network.
Images including railway stations and shopping centres were allegedly found on his phone.
"We confronted him with the video evidence. He had to admit it was him," a police spokesperson said.
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Belgian prosecutors have said Abrini had also told police that he threw the white jacket that he was also wearing at the time of the attack into a rubbish bin and had sold the hat.
A statement said, "He [Abrini] is indeed the third man present at the Brussels national airport attacks. He explained having thrown away his vest [jacket] in a garbage bin and having sold his hat afterwards."