Jurors have been shown CCTV footage said to show the moment two inmates attempted to kill a prison officer.
Brusthom Ziamani, 25, and Baz Hockton, 26, deny trying to kill Neil Trundle in a "terror attack" at HMP Whitemoor, Cambridgeshire, on 9 January.
Prosecutors have said the pair "lured" Mr Trundle to a store cupboard where they launched the assault with makeshift weapons.
Security video appears to show two men pushing an officer through a doorway.
Giving evidence, Mr Trundle told an Old Bailey jury he went to open a store cupboard after the defendants asked him to replace a broken spoon.
As he unlocked the door he saw one of the men in his "peripheral view", he said.
"Before I knew it I was on the floor on my back... I did not know what position I was in but I was on the floor and I was being attacked."
He told jurors he had felt "blows coming down" and fought off "repeated stabbing blows to the head".
The court has previously heard terror convict Mr Ziamani and radicalised Mr Hockton wore imitation suicide belts and shouted "Allahu Akbar" - God is greatest - during the attack.
Mr Trundle, who has been a prison officer for more than 14 years, said he "was too busy trying to survive" to hear what his attackers were saying.
"They were focusing on my head, my neck, all vital organs. They had ample opportunity to stab me in the leg or kick me in the leg but they just carried on with the top half," he said.
The officer told jurors he had not had any problems or "cross words" with Mr Ziamani before.
He said Mr Hockton "follows in the footsteps of Mr Ziamani", and he had noticed him copying his co-accused's "abnormal" behaviour by sleeping under his bed.
Under cross-examination, Mr Trundle denied that he "had it in" for Mr Hockton or had ever asked him why he was "wearing a dress".
Prosecutors alleged the pair used "painstakingly constructed" makeshift weapons and "were motivated to commit the attack by extremist Islamic ideology".
Jurors were told that an alternative count of inflicting wounding with intent in relation to Mr Trundle is available for Mr Ziamani.
The alternative charge need only be considered if the jury acquit him of attempted murder.
Hockton has already pleaded guilty to that alternative offence, thereby accepting that he intended to cause really serious harm to Mr Trundle, but not accepting that he intended to kill him.
Ziamani has pleaded guilty to assaulting a female prison officer and a nurse who intervened in the attack, the court was told.
The trial continues.