http://your.heathrow.com/heathrow-launches-steeper-approach-trial-to-reduce-noise/
To sum up the article, Heathtrow will try to increase the slope angle from 3° to 3,2°-3,5°, allowing for a reduction of noise, and making possible the expansion of the airport and the construction of a third runway.
Trials began on 2015 and are planned to end on March 16 2016.