well M gove cannot be a disinterested party as his constituency Surrey Heath (Camberley and Environs) has a huge degree of interest in LHR with a great number of residents working there or employed by Big Airways .
Of course now hes revealed as Mr beans evil twin there is no telling what he will do since he changed sides on the EU referendum and that was a bigger deal than LHR expansion which he has indicated he favours.
As to airlines moving to LHR from other London airports - Easy maybe for a few business type flights by Ryanair would never move as its just to pricey, same with the others. Also much of the 'new capcity' will in practice be taken up in turning LHR back intoa sustainable operation , ie one that doesn't fall to pieces with any delay due to lack of capacity reserve. Also I can see the owners focus being on more Long haul flights and more high value premium customers. I dont think they want the airport full of drunken hen party groups and blue rinse pensioners of Malta for a cheap winter hol