The world's longest and fastest urban zip wire has just opened in London

The walkie-talkie crackled and I heard the safety instructor behind me say: "Please step back. Do not jump."

Not exactly what you want to hear when you've just mustered up the kahunas to walk the plank off a 35-metre high launch deck, with nothing but a harness and a wire separating you from certain pulverisation.

But this is indeed what happened this morning when I trialled Zip Now's new zip wire in Archbishop's Park near London's South Bank.

Just a safety precaution, apparently, as moments later the instructor's walkie-talkie murmured once again and we received the go-ahead. I leant back, bent my knees, and glided for 225 metres down the world's longest and fastest urban zip wire. The fastest in the world is at Zip World Velocity in North Wales, while the longest (2.8km) is in Ras Al Khaimah in the UAE.

Zip wire aficianados will know that this isn't the first time a line has been drawn across Archbishop's Park - a similar contraption was here last year, although with only two wires. This year, three can "fly" at the same time.

Riders travel at 50kmph (31mph), with views of Lambeth Palace and Parliament to the right, leafy southwest London to the left, and Millbank and Nine Elms dead ahead.

Founder Barry Shaverin said: "Last year's event was so successful we wanted to return for one more year, and have worked hard to make the event fresh for riders that are paying us a repeat visit."

He is referring to the new grand finale, the "Mega Drop", which offers a quasi-bungee jumping experience from the outset. It looks quite tame from ground-level but (believe me) feels slightly terrifying when you're up there and have to take a step out onto thin air.

Zip Now London opens today and runs until early September. Adult tickets start from £22.50, children £16.50 and family and group packages are also available. The ride is open from noon till 8pm. See zip-now.co.