Several companies make backpacks-cum-panniers but Ortlieb make what we think is the best. In its pannier guise, the Vario's shoulder straps fold into the zipped vertical front pocket, a stiff internal backing plate ensuring there’s no disconcerting wobble behind you.
Chest straps keep it in place in its rucksack mode, the wide shoulder straps and rubberised padding ensuring it’s comfortable. It’s made from waterproof nylon, with Ortlieb’s usual high quality construction, has two external pockets, an internal pocket for a 15in laptop with plenty of room to spare. It’s not a quick swap from rucksack to pannier, but it performs well in both modes.