Arnis Zalkalns, 41, served seven years in jail for killing his wife Rudite Zalkains, 22, in his homeland in 1998, according to Latvian state police.
He has now been named as the prime suspect in the case of missing 14-year-old schoolgirl Alice Gross, after being spotted following her in CCTV footage from the night she disappeared.
Neither Zalkalns or Alice have been seen since, although a bag of the young girl's belongings have since been found.
Now the mother of Zalkalns' murderer wife has spoken out, revealing that her "callous" son-in-law served a disgracefully short prison sentence for his crimes.
Speaking with the Daily Mail, the dead woman’s mother revealed that Zalkalns tricked her daughter into going to a deserted forest, claiming they were on their way to pick up a new motorbike he had bought her.
Once alone, he bludgeoned her over the head with a scaffold pole before stabbing her through the chest. He then pushed her body into a grave he had already dug, covering her with soil and leaves.
Zalkalns then toasted her murder by drinking a bottle of vodka as he stood over her shallow grave.
The grieving 70-year-old broke down in tears when she heard that he is the prime suspect in the Alice Gross case.
Speaking from her apartment on the outskirts of Riga, the Latvian capital, she said: “I always feared he might kill again.
“Once you have tasted blood the taste stays and you never stop. He killed our lovely daughter and destroyed our family.
“I’m still angry at the length of his sentence. This was a callous and heartless murder with no remorse. My daughter was trained in karate and she could not fight him off.
“He prepared my daughter’s grave in advance and planted the weapons next to it. Then he tricked her into going to the forest.”
Following his release from prison in 2005, Zalkalns moved to Latvia and started a new family, but, when his wife was warned that she was married to a killer, he moved to London.
UK immigration officials, who had no idea of his criminal past, let him into the country.
Two years later he was arrested in Ealing, west London over an alleged indecent assault on a 14-year-old girl but was never prosecuted because the victim was unable to substantiate her account.
In dramatic developments, police searching for Alice Gross have released new CCTV footage showing Zalkalns cycling along the same isolated towpath in west London that the schoolgirl took just 15 minutes after she walked the route.
Detective Superintendent Carl Mehta, who is overseeing the inquiry into Alice's disappearance, said: ”They were both going in the same direction so it is clear he would have passed her.
“The focus of this investigation is now what happened when this took place.
“It is extremely urgent that we contact Arnis and question him about the matter of Alice’s disappearance.
“We also want to speak to anyone who may have seen him or who may have helped him by giving him money or somewhere to stay.”
Police have issued an all ports and airports alert for the Latvian and urged people not to approach him but dial 999 if they see him.
They also announced a reward of up to £20,000 to anyone with information that leads detectives to find Alice.