After all the academic papers, statistics and political hot air expended on the latest crime fighting initiatives, we are no closer to pinning down exactly why crime rates have fallen. Reuters

Five men and one woman have been arrested in London as part of a pre-planned counter terrorist operation.

The men and woman were arrested suspicion of the commission, preparation or instigation of acts of terrorism.

Three men aged 18, 24 and 26 were detained in east London and a 29-year-old man was arrested in the street in west London.

The 24-year-old man was tasered during his arrest but did not require hospital treatment.

A 30-year-old woman and a 21-year-old man were arrested at separate addresses in west London. All have been taken to a south east London police station where they remain in custody

Metropolitan Police say the operation is not linked to the Olympics and Paralympic games.

Eight flats in north, east and west London and one business in east London are being searched under the powers of the Terrorism Act 2000.

Meanwhile, a computer specialist has been arrested in London accused of helping to provide graphic design expertise as part of a propaganda push by al-Qaeda to find western recruits.

Minh Quang Pham, 29, is said to have sworn an oath of allegiance to al-Qaeda in the Arabian Peninsular (AQAP) after leaving Britain to join the terrorist group in the Yemen in December 2010.

According to the Daily Telegraph, he is said to have received military-style training and helped AQAP with their propaganda efforts before returning to Britain eight months later.