A teenager was held in a headlock and forced to apologise "for being gay" in an attack on an underground train to North Greenwich, say police.

British Transport Police have released images of two people they would like to speak to in connection with the attack.

The 19-year-old victim was in fancy dress along with a group of friends who were travelling on the Jubilee Line train when the offenders boarded at West Ham and began to hurl abuse at the group, using homophobic language.

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A police spokesman said: "When challenged, they became more aggressive. The first offender then pulled the victim from his seat into a headlock, strangling him. The second offender took the victim’s phone and verbally abused him again, also making threats to stab him.

"They demanded the victim apologise for being gay which eventually the victim did as he was struggling to breathe. They then let him go and handed back his phone and a fight ensued between the victim’s friends and the offenders.

"One of the victim’s friends, a 25-year-old woman, was punched and pushed to the ground. She sustained bruising. The original victim did not sustain any injuries."

Police are asking anyone who knows the men in the photos to call them on 0800 40 50 40 or text 61016, quoting reference number 273 of 1/12. The attack happened on October 21 at around 11.10pm.