British Airways has Club World business class on sale for £994 or $1,334 from London Gatwick LGW to Oakland, California OAK in January and February 2018. These fares are only available starting from London for departures.
I find these fares easier to search through Google Flights for finding low fare dates quickly. Monday, Wednesday and Saturday appear to be main departure days from London.
British Airways Club World Business Class
London LGW – Oakland OAK – London LGW