Rebelling against the status quo is "triumphantly admirable", former Metropolitan Police Commissioner Lord Ian Blair has said.

In a speech for Lent to be broadcast on BBC Radio 4, the practising Anglican emphasised the need for conflict as an "essential part of natural and human progress".

Lord Blair, who led the Metropolitan Police at the time of the July 7 bombings in 2005, said: "As a police officer for many years, I have tasted the fear that comes from sudden and unexpected outbreaks of violence and have seen the way it can destroy the lives not only of its victims but of whole families and communities. First century Judea knew all about that.

"And yet we also know that conflict is an essential part of natural and human progress.

"Without the clash of rock and sea, there would be no sand. Without human decisions fiercely to debate ideas, to risk all, to resist injustice and oppression - as we all have seen so powerfully in other parts of the Middle East in recent weeks - to take on and overturn received and complacent wisdom, mankind stagnates and loses sight of its highest purposes.

"From Martin Luther to Nelson Mandela, from William Wilberforce to Rosa Parks in Alabama, the decision to rebel against the status quo remains triumphantly admirable."

In November last year the retired commissioner gave a highly personal speech to the Theos think tank in which he acknowledged religion could be a source of intolerance, but said it was principally a force for good.

The Lent Talks on BBC Radio 4, which begin with Lord Blair on Wednesday March 16 at 8.45pm, will run for six weeks and be repeated on Sundays at 12.30am. Other speakers include the Imam of the Ground Zero Islamic Centre, Imam Feisel.