On this riverside walk we track down the unmarked monuments and buried tubes around Greenwich and the Isle of Dogs. We seek out their stories of power, pollution and danger.

We start by speeding across the Thames by Clipper from Greenwich Pier to Masthouse Terrace Quay. From there it’s a 3 and a half mile ‘dot-to-dot’ walk as we link together the chimneys above our heads, sometimes tracing the routes of tunnels.

Note to budding steeplejacks and subterranean explorers: leave your harnesses, torches and hard hats at home! Apart from the descent into one tunnel, we’ll keep our feet firmly on ground level as we let our minds wander above and below.