You should really plan to fly all the legs you've booked, and include the cost and time of getting to/from Oslo to start and end your trip. Not doing so is hidden city ticketing.

Ex-EU fares seem to be getting more and more publicity, and if an increasing number of people drop the final segment BA may start to impose restrictions from not allowing short checked luggage, asking for the fare difference for no-shows, or removing avios/TP's for all segments. The US airlines are much stricter on hidden city ticketing, it is only a matter of time before BA follows suit..


If you call to change your current booking to cancel the final leg, your ticket will be re-priced to an OSL-SYD-LHR fare.

The fare rules do alloww a free stopover (plus APD) for up to 10 days so you could add a stopover in London and fly LHR-OSL a few days later. However if you've already booked, you will need to pay the change fee.