British Airways has launched a sale offering roundtrip fares to London from $840, including all taxes and fees.The sale runs until December 5, 2012. Customers can travel outbound between November 28, 2012 and December 16, 2012 and from December 24, 2012 to March 24, 2013, giving them a great opportunity to visit London over the holiday period.Roundtrip fares in World Traveller must be booked seven days in advance. Weekend travel is an additional $40 roundtrip. Minimum stay is Saturday night and changes can be made at for $275. Seats are subject to availability.Tickets can be booked through local travel agents, by phoning the toll-free number, 1 800 AIRWAYS, or by visiting the website at www. ba.com