The rucksack bomb that killed 22 people in Manchester was so complex that it could only have been made by an expert, leaked crime scene pictures suggest, as it emerged that an al-Qaeda bomb-maker lived on the same street as suicide attacker Salman Abedi.

Photographs of bomb remnants found at the Manchester Arena show a trigger switch with a tiny circuit board soldered into the end, which experts say could point to a remote-control or timer built into the bomb to ensure an accomplice could detonate it if Abedi lost his nerve.

Investigators believe the bomb, packed with bolts and screws, was contained in a lightweight metal case carried in a black Karrimor rucksack with a blue lining. They also found the remains of a specialist 12 volt battery that is more powerful than high street brands of battery used in previous attacks.