A victim of forced marriage escaped from her husband while she was on her honeymoon.
The British woman alerted officials when she flew back to Heathrow alone.
Her story emerged as Scotland Yard launched an operation at the UK's busiest airport to raise awareness of forced marriage.
Police officers, along with Border Force, are aiming to identify victims and perpetrators of the practice, as well as those at risk of female genital mutilation, honour-based abuse and breast ironing, as they return to the UK.
The operation is part of a national week-long crackdown on forced marriage, dubbed Operation Limelight, focusing on flights to and from countries where the practice is the most common.
Amanda Read, Border Force national lead for safeguarding and modern slavery, said: "A couple of weeks ago we had a case at Heathrow of a girl who had a forced marriage, went on honeymoon and managed to escape from her honeymoon."
She said her husband, who is also British, was intercepted when he returned to the country separately but would not say whether or not a criminal probe is under way.
"It's an ongoing case. For me, it was the first time I had seen that," she said.
"I think it (the forced marriage) had happened here and they had gone out on honeymoon. She was an adult, a young adult.
"I can't remember exactly where she had been on honeymoon. She came and made a declaration when she had come back."
Check-in staff and cabin crew at airlines, including EasyJet, are being trained to spot victims of forced marriage, FGM and modern slavery.
But police stressed airport interventions are a last resort, with the focus on changing attitudes and prevention.
Last year, the Home Office supported victims in 1,764 suspected cases of forced marriage, 574 of which involved under-18s.
These cases were linked to 74 different countries, the most common of which involved travel to Pakistan (769 cases), Bangladesh (157 cases) and India (110 cases).
Officials say real numbers are likely to be much higher because the crime goes unreported.
Polly Harrar, founder of the Sharan Project charity, said forced marriage victims have been identified between the ages of two and 80.