Surprisingly, smiling is not permitted in passport photos.

Passport photographs are rarely incredibly appealing due to the strict rules for what is allowed.

No smiling is one of the requirements for a valid passport, as is keeping one’s hair out of one’s face.

The latter was made possible by the UK Passport Service’s 2005 ban on smiling in passport images.

This is due to the new biometric technology used in passports.

If the person smiles, the facial recognition software might not be able to identify their face.

A Home Office spokesperson told the BBC that “when the mouth is open, it can make it difficult for facial recognition technology to work effectively.”

This is impossible, as user Dan Holliday on Quora explained: “This is because biometric facial scans typically identify 14–20 points on your face (like the edge of your nose, the corners of your eyes, and your lips), but the position of your face alters those points and may make it difficult to identify who you are.

As a result, the biometric system works best when you are calm and unassuming (not frowning or smiling).

The prerequisites for passport photos are listed on gov.uk as “in your photo, you must have a neutral expression and your mouth closed.”

Biometric technology is a revolutionary technique in terms of additional security measures for traveler screening.

The UK might soon have access to cutting-edge technology that would cut the time it takes to receive a passport down to only 15 seconds.

The plan has already been tested in Australia and the Netherlands.

As 123 people enter the UK, border procedures will need to be tightened since Brexit could result in an increase in customs checks from 90 million to 390 million every year.

Airports are under pressure because non-EU tourists get through security in 45 minutes whereas 95% of British and EU citizens do so in under 25 minutes.

The success of Brexit, in the opinion of Chancellor Philip Hammond, rests on “frictionless” borders.