The man accused of shooting dead Ben Purdy choked back tears this week as he told of his failed ambition to join the British Army.
Andrew Bayne, 37, denies he was responsible for the killing but admits he was at the scene and heard a gunshot.
The Rotherhithe resident claims that Ben’s girlfriend’s ex Michael Bagnall, 22, brought the gun to the scene but did not accuse him of carrying out the shooting.
Bayne has been giving evidence with the help of an intermediary because he has learning difficulties.
But prosecutor Crispin Aylett QC suggested Bayne was “pretending to be more stupid than you really are.”
Mr Aylett added: “Anyone who knows you would know you like dressing up in army uniform and had a collection of guns.”
Bayne replied: “Yes they were locked in a cupboard.”
Mr Aylett also referred to Bayne having photos of guns on his phone and his “dearest wish to be in the army.”
Bayne told the court: “I am sorry, I wanted to be a soldier for this country and make my family proud instead of people calling me a spastic.
“My wish in life is to join the army, to be proud I’m a soldier, to be proud I’m British. I don’t want to be a bum.
“They take the p**s out of me every time. It’s not fair, I’m just trying to be normal.”
The judge Christopher Moss QC decided to rise early for lunch as Bayne became emotional.
Earlier Michael Magarian QC, representing Bagnall, suggested Bayne had “a desire to prove yourself” and added: “That’s why you did what you did that day.”
Bayne replied: “I did nothing like that.”
Bayne allegedly murdered the 18-year-old apprentice plumber after intervening in a love triangle dispute involving his nephew.
Bagnall allegedly recruited his uncle, Andrew Bayne, his cousin Reece Bayne, 19, and a 17-year-old, who cannot be named, to track down Ben and his friends.
When they did, Andrew Bayne shot Ben in the head and threatened to gun down one of his friends, the court heard. Ben was pronounced dead in hospital the following day.
Michael Bagnall and Andrew Bayne, of Alpine Road, Rotherhithe, Reece Bayne, of Concorde Way, Rotherhithe, and the 17-year-old, all deny murder.
Michael Bagnall, his 19 year-old sister Lee-Ann Bagnall and Anthony Bayne, both also of Alpine Road, Rotherhithe, all deny affray relating to an earlier confrontation.
Michael Bagnall, Reece Bayne, and the 17-year-old all deny conspiracy to commit assault occasioning ABH.
Andrew Bayne denies possession of a firearm with intent to cause fear of violence.
The trial continues.