Headline lowest fares would be £999 Business / £1500 First to India ( BOM & DEL ) / East Africa ( NBO & DAR ) .. other destinations also avaible in Asia, South America & Africa
Details on here
https://www.swiss.com/unitedkingdom/en/Offers/LHR ( similar prices from other UK airports ) .. Book by 02SEP valid for travel until Summer 2019 .. no mention of blackout periods , but guess dates may be difficult for availability at peak times.