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!
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!