Who is No 1 from cruise leve?

[GMS]

Flying to Tenerife last night at FL330 I had a spanish aircraft ahead at a constant 5 nm at FL370 approaching descent point.
Initially we were both going to the same point, GANTA, but I was then instructed to turn away for separation.
Who has priority as far as ATC procedures are concerned? I can only presume there is a laid down procedure in your manuals.
As I speak spanish I was about to tell the controller what I thought of his handling of the situation, it cost us about seven extra minutes, but decided that the RT was not the appropriate medium.
I know some countries ATC agencies give their nationals priority, but I would like to know the procedures so that next time I may put my foot down.
I would appreciate any controllers comments.

[ATC Watcher]

The general rule is "first come, first serve"
The specific rules however vary for each ATC facility, because we base our clearances on safety of course, but next on expedition, and sequencing.
Clearances can also depend on your type of a/c ( speed and performance), altitude and most importantly how you fit in the picture vis a vis other traffic.
In other words even if you are number 1 it might make a lot of sense for ATC purposes to delay you. In my Facility we always take traffic expedition before perceived "priority" of aircrew.
In your specific case there might have been other traffic at 370 affecting the other, meaning to solve a later conflict it made sense to turn you away. Especially if the other one has a faster TAS than you.
It is extremely difficult from a cockpit to derive the ATC picture, especially nowadays where frequencies are combined and you, in the air, only hear half the transmissions.

[GMS]

Many thanks for your repply ATC Watcher. You are right, there may have well have been somebody else I was not aware of. I'm glad I didn't let off steam on the RT.

[GMS]

Many thanks for your repply ATC Watcher.