The man accused of driving a van into a crowd of people near a north London mosque had hoped to kill Jeremy Corbyn.
Darren Osborne, 48, has denied he was behind the wheel during the attack on 19 June 2017, telling Woolwich Crown Court a "guy called Dave" was driving.
He said they originally hired the van to kill the Labour leader on a march he was expected to attend.
Mr Osborne also said that it "would have been even better" if London Mayor Sadiq Khan had been present.
"It would have been like winning the lottery," he added.
Mr Osborne is accused of mowing down people in Finsbury Park, killing Makram Ali, 51, and injuring nine others.
He denies charges of murder and attempted murder.
Taking to the witness box, Mr Osborne said he met Dave at a pub in Treforest, South Wales, in early April or March last year, while he also met a man called Terry Jones, and that the trio discussed their political views.
Mr Osborne said they initially planned to murder a Labour politician in Rochdale, before planning to target Mr Corbyn, believing he would be at the annual Al Quds march in London.
He told the court he was alone in the van as he drove towards the march - but that "road blocks" in central London had "thwarted their plans".
Later, he said he travelled to the Finsbury Park area, because "it was Jeremy Corbyn's constituency", where he met the others.
Mr Osborne said they swapped drivers and he was "in the footwell" while Dave was driving, adding he had "no idea" where Dave went after the collision.
He said the opportunity to attack the Labour leader would mean "one less terrorist off our streets".
Asked if he had contact with Terry and Dave after the attack, Mr Osborne told the court they were planning to form a far-right group, adding: "We were going to call ourselves the 'Taffia'."
Earlier, the court heard evidence on whether Mr Osborne acted with accomplices - namely two men, known only as "Dave" and "Terry Jones".
Concluding the prosecution case, Jonathan Rees QC said Mr Osborne told the Metropolitan Police on the day of the attack that he was acting alone.
He read a statement from Det Con Paul Dring, who interviewed Mr Osborne as he was under armed guard at University College Hospital, on the day of the attack.
During the interview, Mr Osborne told DC Dring: "I'm flying solo", the court heard.
'Couple of pints'
Mr Osborne is said to have spoken to officers after he was detained and told them he "lost control" of his van.
The court was shown footage from the body camera of PC David Jones, who is said to have handcuffed Mr Osborne while he was on the ground after the incident.
A man - who the prosecution says is Mr Osborne - can be heard saying: "I lost control of the van", and "lost control, man".
Mr Jones then says: "Were you driving, yeah?" and the man is heard to reply: "Yeah".
Asked if he had been drinking, the man said he had consumed a "couple of pints".
Mr Osborne denies the murder of Mr Ali and attempted murder of "persons at the junction of Seven Sisters Road and Whadcoat Street, London".
Mr Ali, from Haringey, had collapsed at the roadside shortly before being hit by the vehicle after leaving a prayer meeting.