VS43 departure time

It seems that the departure time of VS43 is changing.

Now:
Dep LGW 10.45
Arr LAS 13.30

Changing to:
Dep LGW 11.25
Arr LAS 13.40

Anyone know why this has changed and how they've been able to reduce the time by 30 mins? Every time I've flown on the 43, even when pushing back around 10.45am, it seems to struggle to arrive on time!

I have done this route about 15 times, and if it leaves LGW on time, it mostly seems to arrive early into LAS, I guess the artificial flight duration that has been used so that VS get a good "on time" rating has been decided to be a bit to generous!!!