Adding a return flight to an existing companion voucher booking

[LHRNAIAOSL]

Hi, I have an existing companion voucher return flight booked LHR-HND and HKG-LHR for two adults and a lap infant in CW both ways. We’re now planning a LHR-OSL return flight to take place right before the existing booking. Would it be feasible and beneficial to add the LHR-OSL return legs (in Club Europe) to the existing booking for more Avios / ADP savings given it’s a companion voucher booking? The new booking would then be LHR-OSL-LHR-HND x HKG-LHR. Not sure if this is within the rules of the CV, and whether there would be any benefit if so.

[JDB]

You could start the journey in Oslo (and thereby only pay the Avios for one person also for that leg) but you can’t tack on a return trip London to Oslo in front off the long haul. There will only be an APD saving if you travel OSL-LHR-HND on a connection, i.e. continuing to Tokyo within 24 hours.