London - It is a journey that takes more than 20 hours by conventional passenger plane - enough time for several meal breaks and a string of movies.
But soon British holidaymakers will be able to touch down in Sydney having barely digested their lunch.
Flights from the UK to Australia could be reduced to about four hours thanks to new engines developed in Britain, experts say.
Rocket engines capable of propelling an aircraft to Mach 5.5 – five times the speed of sound – are being developed for use on commercial airliners by Oxfordshire-based firm Reaction.
Dr Graham Turnock, of the UK Space Agency, told the Space Conference in Newport: "This is not sci-fi. This is not a pipe dream. This is literally in the works. It has the potential to turn air travel on its head. Certainly the way you conceive air travel will completely change in ten years’ time."
The SABRE – Synergetic Air Breathing Rocket Engine – has a top speed of 4,143mph, meaning the approximate 10 550 miles between the UK and Australia could be covered in just four-and-a-half hours. Dr Turnock forecast that the technology for an operational flight vehicle could be ready by "the 2030s".
The revolutionary technology overcomes one of the key problems of ultra-high-speed flying. Usually, when flying at such a pace, the air entering the engine would reach temperatures that would melt the parts.
But the SABRE will use liquid gases such as helium which, during tests, have been able to cool the incoming air from 1 000C to -150C in one hundredth of a second – without creating ice blockages. Concorde got around the problem using air vents to slow down the air reaching the engine.
Hydrogen will also be used to power the SABRE. It is considered a green fuel as it produces water vapour when it burns as opposed to greenhouse gas carbon dioxide.
It has been previously suggested that the design could power a generation of passenger jets called the Lapcat – which will travel at about two-and-a-half times faster than Concorde’s top speed. And while normal long-haul passenger jets cruise at around 35 000ft, the Lapcat could fly as high as 92,000ft.
Shaun Driscoll, of Reaction, said the system could also be used to "take off on a runway, go into space, release a satellite and come down".