When a motorbike convoy of Boko Haram fighters invaded Baga in north-east Nigeria last December, residents feared the very worst. Watching the gunmen roll in, they recalled Boko Haram's last seizure of the town in 2015, when hundreds of their men were slaughtered and their women kidnapped as “bush wives”.

This time, though, the Hells Angels' style motorcade did not bring the usual orgy of rape, murder and pillage. "They didn't beat anyone, they just said that we should stay where we were," said Mansour Yusuf, 44, a father of nine. "But they also said we were free to leave if we wanted to."

Mr Yusuf took no chances, fleeing along with thousands of other Baga residents to the better-defended town of Monguno, where Nigerian troops have dug a protective trench around the town.

That he is alive to tell the tale, however, does not speak of any new tender-heartedness on Boko Haram's part. Instead, the "hearts and minds" strategy is all part of the long-term game being played by the new Isil-allied faction of Boko Haram.

Known officially as Islamic State's West Africa Province, or ISWAP, the group has gained a firm foothold in the past year, confounding claims by President Muhammadu Buhari that the insurgency is facing defeat.