Heathrow has finished the replacement of asphalt on the southern runway surface.

Completion marks an important stage in the airport's £20 million plan to repair and replace the runways.

The next step is to install some 130,000 metres of cable for over 1,000 aeronautical ground lights, which began at the beginning of August. These lights, placed within the surface, are important for landing in difficult visibility. Once these are completed, flight tests will be carried out to ensure they work.

So far, 22,000 tonnes of asphalt has been laid. Maintaining a smooth surface is an important part of airport safety.

The previous month's weather also threatened progress. Senior project manager Andrew Mitchell said: "During the July heat wave, we had to reorganise our schedule as it was too hot for the asphalt to be laid".

Work is carried out at night, after the last plane lands until the first flights are due to move, to avoid unsettling operations. To further minimise disruption, one runway is focused on at a time.