For one day only a zip wire is to be erected across the River Thames from St Thomas' Hospital to Victoria Tower Gardens to raise money for the Evelina London Children's Hospital.
On Friday 2 December firefighters will rig up a zip wire for the one-off daredevil stunt which aims to raise at least £1 million for Evelina London Children's Hospital.
There are spaces for 20 of the hospital's most dedicated supporters to pledge £50,000 or more each to take part in the exhilarating river crossing.
The event is also part of London Fire Brigade's 150th anniversary celebrations.
The stunt is the brainchild of London Fire Brigade Deputy Assistant Commissioner Andy Roe, whose son Zaki, aged nine, was treated at Evelina London Children's Hospital. He said: "My son might not be alive today if it weren't for the NHS, especially Evelina London, so I wanted to find a way to thank the remarkable staff at this fantastic hospital.
"During the many hours I spent by my son's bedside, I realised that I could use my specialist skills to rig up a zip wire from the roof of the hospital across the Thames and that perhaps people would pay for the chance to speed across it like a firefighter."
"I've got to warn you, this is not a trip for the fainthearted. It will feel like you are flying directly into the Houses of Parliament. There is no other white knuckle ride like it in the world. It's great that I have a chance to showcase our firefighters' skills as part of the celebrations for the London Fire Brigade's 150th anniversary.
"And there's no better way to support one of the leading children's hospitals in the country in helping them to continue their vital work."
The money raised will go towards the £2.7 million needed to build a dedicated Clinical Research Facility at Evelina London. This new facility will allow vital research to improve treatments and cures for numerous conditions including autism, epilepsy, congenital heart disease, kidney disease and allergies.
Details of the event are at www.evelinazip.org.uk