An Evening Standard article reports a total of 13 high-risk airprox incidents involving planes inbound or outbound at London airports last year: 10 at LHR, two at LCY and one at STN. These were "category-A" incidents, with a “serious risk of collision.”
There were an additional nine incidents with Heathrow flights where safety “may have been compromised” among a total of 36 incidents involving passenger planes over London in 2016.
Overall, the number of drone incidents involving Heathrow planes nearly quadrupled from seven in 2015 to 26 last year, according to reports by the UK Airprox Board.
Complete article here