Made for Brompton by Ortlieb, this durable, seam-sealed front bag is completely rainproof. It doesn’t use a roll-top closure, though – the front ﬂap folds over and buckles down – so it might be only 99 percent waterproof in circumstances such as horizontal rain.
It has a 20-litre capacity, with a laptop pouch and organiser pockets inside, and two outside roll-top pockets, large enough for 750ml water bottles. These are removable and one has ﬁxing points for attaching it to the main bag’s clip-on shoulder strap, so it can be used as a valuables bag if needed.
Despite reﬂective logos front and rear, the O Bag still looks businesslike in black (less so in the optional pink). You’ll need a Brompton front luggage block (£15) to attach it to the bike, but not the Brompton bag frame, as the bracket is integral here.
This is an expensive package nevertheless: the waterproof Carradice CarraDry City Folder costs £90, factoring in the bag frame, and it’s more capacious. We think the O Bag is more suitable for use as a briefcase or day bag.