Followers of Islamic State may be hiding their fanaticism by drinking alcohol, visiting bars, and otherwise embracing secular life in a bid to remain under the radar before they strike.

Two of the terrorists who perpetrated attacks in France over the last fortnight appear to have allayed suspicion in this way. These falsehoods to avoid being spotted or pursued by Western intelligence agencies may be linked to the Shia practice of so-called ‘Taqiya’, where lying and concealing faith are permitted under Sharia law for the sake of propagating Islam or defending their own lives in the long-run.

The uncle of 19-year-old Adel Kermiche, one of the terrorists who beheaded Catholic Priest Father Jaques Hamel while he was celebrating Mass yesterday, has told local news that his nephew appeared to have renounced his strong religious beliefs over the last few months, leading to the family relaxing their surveillance of him.

Kermiche had been fitted with an electronic tag and was being kept under house arrest after twice attempting to enter Syria, but his uncle said that, following his second failed attempt, he appeared to be abandoning his former belief.

“Since his release from custody, he seemed to me to have regained his wits regarding his religious beliefs, which were really radicalised before,” he told RMC.

“He seemed to me to be a little more ‘awake’. He was less stubborn and narrow-minded, it seemed to us, than he was during his journey to try to reach Syria. So we had given up a bit on his surveillance.

“Despite wearing an electronic bracelet, we thought he was getting back to normal life, the life that all young people lead,” he said.

In fact, Kermiche appears to have been planning an attack. The church at which Father Hamel was leading Mass when he was killed was on a terror hit list held by another Islamic State-affiliated terrorist who was arrested in Paris in March.

But his family were not the only people deceived by Kermiche. Despite mixing with other terrorists while in prison, Kermiche was released in March after telling a judge: “I am a Muslim grounded in the values of mercy, and goodness – I am not an extremist.” Instead he claimed to have been suffering from mental health problems, insisting that he could not get up in the morning before saying prayers, and that he only wanted “to get my life back, to see my friends, to get married”.

Despite the prosecution insisting that he still posed a risk, the judge allowed him to be released on the grounds that he wear an electronic tag in the afternoons. He carried out his attack in the morning.

Similarly, Mohamed Lahouaiej Bouhlel, who two weeks ago ploughed a truck through a crowd celebrating Bastille Day in Nice, killing 84 men, women, and children, was initially described as non-religious.

Neighbours described the 31-year-old as a loner who liked salsa dancing to pick up women, smoking shisha with other Tunisian immigrants, and possibly engaging in an affair with an older man. All agreed he was indifferent to religion.

However, as days passed it began to emerge that the attack had been planned for up to a year, and that Bouhlel had accomplices.

Paris Prosecutor Francois Molins announced that investigators found images in Bouhlel’s phone dating from last year appeared to show that he was already planning for the attack, while a search of his computer turned up information on Captagon, a drug used by some jihadists before an attack as well as screenshots of another vehicle attack.

Bohlel is also said to have expressed support for Islamic State’s territorial claims, and to have acquired weapons through acquaintances – all without drawing attention to himself thanks to his secular cover, Associated Press has reported.

When police investigated him for a potential road rage incident earlier this year, they found no reason to flag him for terrorism.

A French security official has since suggested that Bouhlel may have been intentionally hiding his faith, following Islamic State suggestions to followers in the West that they hide their radical faith to stay off police radar.

According to the official, attackers who targeted Paris and Brussels in 2015 and 2016 are believed to have done the same.