Get a grip people
The Air Navigation (No 2) Order 1995, Article 59A states:
- No person shall while on an aircraft:
a, use any threatening, abusive or insulting words towards a member of the crew
b, behave in a threatening, abusive, insulting or disorderly manner towards the crew of the aircraft; or,
c, intentionally interfere with the performance by a crew member of his duties
The disturbance, hissy fit, tantrum or whatever else you want to call it was already going before the police were called - this was the reason why they were called in the first place. It is unlikely they'd have known the nature of the dispute, nor who was involved, until they'd arrived and they'd probably have cared even less.
Unfortunately, as in so many of our town centres, borish drunks, quarelsome couples and obnoxious scumbags have become a common problem on aircraft and at Heathrow in general. This is precisely why Article 59A was introduced in Sept. 1999. This law is strictly enforced for good reason, as you'll know if you've ever had the misfortune of witnessing an abusive argument or brawl at 30,000 feet.
The flight crews work for their airlines, not BAA, they are not personally responsible for hold luggage movements let alone the running of the airport (nor for that matter are the police). Flight crews will not tolerate anyone going 'off-on-one' prior to takeoff and will invariably call upon the police to exclude such persons, regardless of how 'understandable' someone's predicament might be.
For their part, the Police will initially ask the person to exit quietly (a confined airframe is no place for a scuffle), it does not necessarily follow that every individual will be prosecuted, they are just required to get off the aircraft as calmly and quietly as possible. In minor incidents the Police often advise the ejectee how best to pursue civil redress and obtain compensation. As is usually the case, the ultimate arbiter of deciding an officer's response is the ejectee themselves, such incidents are both common and extremely tedious.
I would say that someone spitting in your face is both grossly offensive and disgusting in the extreme, it most certainly is an assault. I wouldn't like it, I doubt that you would too; especially when all you're trying to do is your job and you're not even remotely responsible for the situation that gave rise to the dispute in the first place. Spitting is invariably adopted by those who intend to be deliberately provocative and offensive, it has little defensive value - though quite good for courting publicilty (sorry guys, a little harsh perhaps?).
Whatever sympathies you may have for this woman's plight, her response and behaviour towards it was both childish and unneccessary. Can you imagine if we all reacted in this way:
"Hello, my workstation's not working!"
"Sorry, the server's gone down"
"Why?"
"Dunno just yet"
Scream, cry, shout, stamp swear ...... spit
Its pathetic!
PS And yes, the Police will arrest everyone on suspicion of an offence, as someone above correctly ponted out - they have little choice in the matter.