The last message Khalid Masood sent before the attack in March explained he was seeking jihad revenge

The last message sent by the Westminster terror attacker declared he wanted to wage jihad in revenge at military action in the Middle East, it has emerged.

A MailOnline exclusive revealed Khalid Masood was found to have been active on messaging service Whatsapp just two minutes before he carried out his fatal attack on March 22.

But end-to-end encryption meant authorities have struggled to find out what he sent before he careered his hired car into pedestrians on the Westminster Bridge before attempting to storm Parliament.

However, the Independent has learnt that spies have managed to crack into the message, and revealed his motivation was revenge at western military action in the Middle East.

The website reports the person who received the message was extensively questioned, but freed after the police and MI5 concluded that he was not part of a plot and had no prior knowledge of what happened.

Tonight, his Whatsapp still showed he had not been active since March 22, implying spies have cracked the service instead of accessing his messages through his phone.

Masood killed five people and injured 50 during his rampage on Parliament last month.

Khalid Masood's WhatsApp profile shows he has not been online since March 22, the day he died as he took the lives of several others

Police have struggled to get into the attacker's messages because of end-to-end encryption, but say the technique can be replicated

The attack on Westminster Bridge killed five people, including hero police officer Keith Palmer who acted as the last line of defence

Among those were hero police officer Keith Palmer, who was stabbed outside the House of Commons as he acted as the last line of defence.

Security sources have called getting into the message a result of 'human and technical intelligence'.

The sources have not disclosed how they went about the task, but have confirmed the technical expertise now exists for any future replications.

Masood's phone was recovered after he was shot dead by police in the capital.

Masood, 52, born Adrian Elms in Dartford, Kent, was on Whatsapp at 2.37pm approximately two minutes before ploughing into people on Westminster Bridge and four minutes before he was shot dead by armed officers outside the Palaces of Westminster.

The attack carried out by Masood killed five people and injured 50

Two weeks ago, the Mail On Sunday reported that Masood told a family member in a phone call a week before the attack: ‘You will soon hear of my death, but don’t worry… I will be in paradise.’

Khalid Masood’s words appeared to voice the belief held by most interpretations of Islam that only martyrs are guaranteed to enter paradise after death.

According to the Independent, it is not known when the Home Secretary was told about the message being cracked.

She had previously called the encryption on Whatsapp, which made the job tough for security forces 'unacceptable'.

London was thrown into panic again on Thursday, when a man was arrested near the House of Commons with a bag of knives.

Just five weeks after the Westminster terror attack killed that five people, a team of officers swooped and arrested a bearded man dressed all in black shortly before 2:30pm.

Witnesses said the man, who was wearing a tracksuit and trainers, was crossing Whitehall amid the usual crowds of tourists and political staff when a police car suddenly pulled up and officers confronted him.

A large number of armed police then flooded the area as the suspect was pinned to the ground just yards from Downing Street. He was held against a wall of the Treasury before being taken away in a van to a police station.

Security sources say police were tipped off by the man's family, which may have allowed officers the chance to detain him before they had to resort to opening fire.

Parliamentary authorities said they could not comment on what changes had been made to security measures at the Palace of Westminster since the March attack.

In the aftermath of the assault, authorities have reviewed how to keep the area as safe as possible.

Armed police officers have been more visible patrolling the Palace of Westminster since the attack, which also left Masood dead from gunshot injuries.