A missing persons expert said Levi Davis' disappearance in Spain was "more complicated", in part due to diminished information-sharing between UK and European police forces after Brexit.
The case of the former rugby star and X Factor Celebrity star is now being looked into by a specialist criminal investigation unit in Spain, after the former Bath and Worthing rugby player went missing in Barcelona in late October
Levi is still officially listed as a missing person, but the Spanish unit is working to establish whether there was criminal activity involved.
Charlie Hedges, formerly of the National Crime Agency, said complications were “amplified” with international cases.
Mr Hedges, who set up a police expert network for missing people across Europe, said additional challenges included language challenges and different judicial systems as well as European countries having a different style of police operation.
"The primary responsibility for Levi’s disappearance sat with the Spanish police, as this was where he went missing," Mr Hedges told the BBC's File on 4.
With Brexit came the loss of a centralised information system where it was possible for UK police to flag a missing person or a wanted person, and have it automatically flagged to all police forces across Europe.
The European Union Security and Justice Sub-Committee's report 'Beyond Brexit: policing, law enforcement and security' highlighted that after Brexit was finalised, the UK "will no longer have access to the Schengen Information System".
The system had previously been used "extensively", the report said, to "obtain real-time information about the movement of criminals, missing persons and objects of interest".
Hedges added: “We have to revert to the traditional method of notifying Interpol, which can issue a yellow notice to warn police forces in other countries about a missing person and they will facilitate communication between the two countries."
According to figures from the foreign office, about 600 British people go missing overseas every year.
The Catalan Police has now said the case surrounding Levi's disappearance contained "disturbing" details with "no logical explanation" for him going missing.
But the police, also known as Mossos d'Esquadra, were prevented from sharing any more information publicly because of Spanish law.
Levi arrived in Barcelona on October 29 by boat after spending time with a friend, Richard Squire, in Ibiza from October 17.
The pair worked on songs together on the famous party island - Levi recently signed a record deal - and last saw each other when Richard dropped him in Ibiza Town.
Suddenly Levi sent Richard a text message informing him that he was travelling to Barcelona, to go and "see some mates".
Concerned, Richard asked his friend, who appeared on Celebrity X Factor in 2019, to call him when he got there.
Richard said: "So then I sent him a voice note saying: 'You're worrying me. Please tell me where you are'."
After no contact, Richard was forced to inform Levi's friends and family before an official investigation was launched on November 8.
One of the rugby player's last known sightings was at a bar, the Old Irish Pub, in the city centre. Contact was also made on October 30, a few minutes past midnight in a WhatsApp voice note.
In the recording, Levi said Barcelona was "absolutely beautiful" and that he was "getting all my inspo" from it.
Little information about the disappearance has been confirmed or made public since.
The family has also hired a private investigator.
Investigator Gavin Burrows tweeted that he believed Levi was being blackmailed and that this began shortly after his X Factor appearance.
He said: "Following Levi Davis' case being brought to light, we have received valuable alleged information from a number of former participants and other fellow contestants over a number of years, in the X Factor programme, who have confirmed the claims made in Davis' video seem to be true."
Burrows was referencing a now-deleted video in which he claimed he was filmed performing sexual acts on people after being drugged.
Levi's passport has since been found by the port in Barcelona, leading Burrows to speculate that Levi might have drowned.
