Mahmood and Dart were both given extended sentences and will serve two-thirds of their prison terms rather than half, and will spend five years on licence.
Dart refused to stand when he was sentenced, saying: "I don't wish to stand up, I believe ruling and judging is only for Allah."
The judge said that they were all "committed fundamentalists" who would have been prepared to kill.
He told Dart and Mahmood:
I'm satisfied to the required criminal standard that neither of you had ruled out an attack in the United Kingdom, and that you, Mahmood, were looking at arming yourself with a bomb.
Three British Islamic extremists including a white Muslim convert and a former police community support officer have been jailed for terrorism.
Richard Dart, Jahangir Alom and Imran Mahmood, were sentenced at the Old Bailey for engaging in conduct in preparation of acts of terrorism.
Dart was jailed for six years, Alom for four years and six months and Mahmood for nine years and nine months.
Mr Justice Simon told the trio they held "radical Islamist beliefs and have shown yourselves to be committed to acts of terrorism".
They admitted the offence between July 2010 and July last year at a previous hearing last month.
White Muslim convert Richard Dart, 30, was jailed for six years at the Old Bailey today for terrorist offences. He refused to stand as he was sentenced.
Three men are facing lengthy jail terms for terrorism.
Richard Dart- a Muslim convert living in Ealing- and his co-conspirators Jahangir Alom, from Stratford and Imran Mahmood from Northolt admitted engaging in conduct in preparation of acts of terrorism.
They pleaded guilty to committing the offence between July 2010 and July last year.
Dart and Alom travelled to Pakistan to try to get terrorist training, and took advice from Mahmood who had already visited the country.
They'll be sentenced at the Old Bailey later today.