I bought a second hand Brompton bike a few months ago, and it's improved my life manyfold! Living in a very small space (a narrowboat), it means I can easily store my bike indoors keeping it safe both from theft and the elements.

Then carrying stuff became an issue. When I started off my mum was kind enough to lend me her Brompton-bag. These are amazingly sturdy, well designed and durable pieces of kit, and their price tags reflect this. Not wanting to part with more money or sacrifice precious storage space (again, narrowboat), and owning 8 Ortlieb panniers, I knew there must be a way to adapt one to fit a Brompton. And that's what this instructable is about.

Here's a breakdown of the pros and cons of the final result, before you get started

Pros:

With Brompton bags costing upwards of £80, you can save £60 or more if you already own a pannier

No modifications to pannier needed - can still be used on a normal bike rack

Ortieb panniers are 100% waterproof (Brompton bags need the included rain cover to be waterproof)

Ortieb pannier offers slightly more carrying capacity

Cons:

Slightly taller bag means you can only turn handlebars approx. 45º either way. This doesn't affect 'normal' cycling - it only becomes an issue when weaving through traffic, or restrictions in shared cycle/pedestrian areas. And doorways. you can't have your bike light on the lower part of an 'M' handlebar



No backwards-facing compartments

I've kept this instructable quite vague so that it can be used with any type of pannier. Its main purpose it to show people that it can be done, what materials to get and what to expect.