Impact!

A large chunk of rock is presently being plotted across space, on a course to impact with the city of London and the scientists involved in tracking this asteroid are, at this moment in time, actively engaged in seeking out some means at their disposal with which to divert it from its chosen path. A high-intensity laser-beam is tried but to no avail and then, just when the cause seems lost, news breaks of a 'repelling-beam' machine invented by a now-dead professor. YOUR task is to locate this machine and if possible to utilise it to deflect the asteroid and thus save the city of London from certain destruction... Can YOU do just that?