Yonks ago at Heathrow there was an ATC Supervisor who was most keen for his controllers to practice their SRA skills. We, being lazy bu**ers were always "forgetting". He fixed this one morning as soon as we arrived on watch (7am) by ringing the tels department and had them turn off the ILS on both runways! We spent the rest of the morning doing SRAs in crappy weather!
I doubt that's the reason at Gatwick... but you never know!