If the government sticks to its ludicrous "no new rwys in the south east", this may be the only option!
There is, of course, the problem of a reservoir in the way for the lengthening of 09R/27L unless the resultant "four" rwys are considerably shorter than at present.
One may have expected some safety constraints, but as it is proposed by a former BA pilot who would know LHR inside out, perhaps these are not as significant as the less experienced might think.
Suspect that the biggest stumbling block is that it will mean permanent mixed mode operations and the end of flightpath residents' daily half-day of quiet.
Expect that HACAN down at Clapham (or is it vauxhall?) are "on
manoeuvres" already!