Originally Posted by
Zembla
I think that the difference can made because a UK-AMS-Elsewhere is potentially cheaper than AMS-Elsewhere.
If the journey is without stopovers (i.e. never leave the airport at Amsterdam), yes, absolutely.
In my experience, though, once you use the "Multi Stop" facility on the KLM website, it starts selecting from higher fare buckets only - the prices are always far, far higher than you would expect.
And buying a multi-city or multi-stop ticket won't absolve the OP from having to pay the full UK APD if the ticket originates in the UK.