The detective who led the probe into Zara Aleena's murder has revealed how police caught her killer.

Det Ch Insp Dave Whellams described how Metropolitan Police officers moved in to arrest sexual predator Jordan McSweeney, 29, while he slept in a caravan at a fairground – just one day after he murdered Zara.

The 35-year-old law graduate had been targeted by McSweeney, from Dagenham, in the early hours of June 26 as she was walking home in Ilford.

McSweeney dragged Zara into a driveway, sexually assaulting and murdering her.

He was sentenced at the Old Bailey on Wednesday (December 14) to life imprisonment and told to serve at least 38 years. 

Barking and Dagenham Post: Jordan McSweeneyJordan McSweeney (Image: Met Police)

DCI Whellams said his mind began racing back in June as soon as he was given the basic details of the case he and his team were to take on.

He said: “It was a stranger attack so there is no suspect per se. It is a case of whodunnit.

“I have to decide the priorities and where I think the best possibility of wins can be achieved, whether there is CCTV, whether there is forensics, wherever there is house-to-house or witnesses that may have seen something.”

Take a look back at our live blog of McSweeney's sentencing.

Working backwards from the crime scene, officers recovered grainy CCTV footage of the attack on Ms Aleena and the minutes that led to it.

DCI Whellams said: “We pick Zara up in Cranbrook Road. He is behind her for a considerable period of time. We’re talking hundreds of yards.

“There comes a point where he catches up with her and he must make his mind up that he is going to attack whether he thinks there’s nobody around or whatever.

Barking and Dagenham Post: Zara AleenaZara Aleena (Image: Met Police)

“He jumps on her and he drags her into a front garden. It’s absolutely shocking.

“He’s in the front garden of a house, a residential house, where people are in. There would have been an altercation, there would have been a lot of noise but he wasn’t worried about that. He just single-mindedly wanted to attack.

READ MOREZara Aleena's aunt speaks out as Dagenham killer jailed

“You get the sense of the ferocity of the attack, how brutal it was. And it was brutal. And it was sustained.

“We’re talking about a grown man of proportionate size against a small, slightly built woman who had no idea – this was completely out of the blue.”

By tracking the killer’s movements on CCTV, police were able to circulate a clear image which produced around half a dozen possible suspects.

A forensic examination of the scene also uncovered a fingerprint in blood which, due to the poor quality, initially failed to provide a match on the national database.

However, details of the six potential suspects were sent to a fingerprint expert who compared each one and came up with a positive match to the bloody print.

DCI Whellams said: “The fingerprint expert said that’s a match for Jordan McSweeney, and that was it. That was a crucial piece of information.”

Officers retraced the attacker’s route from Cranbrook Road to a fairground in Valentines Park.

When they went to make the arrest, McSweeney appeared “confused” and “dazed”.

In his police interview, he remained silent and gave no explanation or sign of remorse when shown the CCTV.

But an examination of McSweeney’s caravan and the fairground provided further overwhelming evidence.

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It included a bag deposited under the skirting of another caravan containing his bloody clothes and shoes.

DCI Whellams said McSweeney had been driven by a desire for sexual gratification and had shown no remorse.

The senior officer said: “He can only be described as a danger to women. His very demeanour, the way he is, the focus that he has and his don’t care less attitude.

“He is somebody that we really can’t allow out on the streets.”

CCTV from earlier in the night showed he had stalked two other women after leaving a bar drunk and possibly high on drugs.

The footage showed him lurching in the road and almost being run over by a car, before he spotted a lone woman.

DCI Whellams said: “The first thing that you get from this particular case is McSweeney’s determination, his focus.

“We see him following at least two females before the attack on Zara. And he’s persistent. The worrying thing for me is he’s not put off.

“These females become aware of his attention and they decide to take evasive action, they come into shops, they run down roads, they run past their own address, rather than go in.

“But he is not put off. He then moves on to another and he moves on to Zara.”

McSweeney had been released from prison on June 17 and his licence was revoked after he missed probation meetings.

Some 24 hours before the murder, police went to his family address but found he was not there.

DCI Whellams said: “As far as I’m aware, the police did as much as they could do with what they knew at the time.”

Reporting by PA.