According to today's MailOnline, happened on July 22nd this year:
Heathrow Airbus in near miss with drone that ghosted into Britain's biggest airport undetected by air traffic control | Daily Mail Online
A bit short on details (the Category A incident is listed in the index on the UKAB's website, but the report itself isn't yet up), but the coordinates suggest an aircraft on final approach to 09L with an altitude of 700ft quoted.