On 29th May 2019, the CAA published a policy update and further consultation (CAP1782) on the economic regulation of capacity expansion at Heathrow.  This consultation will run until May 24th 2019.  It is a follow-on document to CAP1722 published in October 2018 and both documents may be seen here.

CAP1722 October 2018

CAP1782 March 2019