The Saudi ADV Tornado's were brought since at the time, (1985), the US, under pressure from Israel and it's lobbyists, were campaigning against further F-15 purchases.
They had to fight hard to get the E-3 and tanker aircraft too.
Consider the task, a huge, very sparely populated landmass with potential enemies to the north, east and west of them.
While the F-15's were capable enough here, clearly the Saudi's felt that more fighter/interceptor aircraft in that basic class were needed, now Washington was becoming problematic it seemed.
At the time, the Iran-Iraq war was running and on, raising tensions further.
The Mirage 2000 was a fine enough aircraft, but did not have the endurance for covering this vast area.
(Dassault tried to get the Saudi's to fund the scaled up, twin engined Mirage 4000 one of which was flown as a prototype. Whatever the Saudi's thought of that, clearly an operational Mirage 4000 would be years away).
The Saudi's also wanted to bolster their attack capability, based back then on F-5E's.
Try getting a longer range bomb dropper past the Washington lobbyists though!
So the Saudi's turned back to those who had originally put Saudi Arabia into the supersonic jet game 20 years before, with BAC Lightnings.
They also still provided the trainers, both aircraft and people.
So in getting the Tornado IDS, also getting a version which had powerful radar, heavy armament and plenty of range and endurance, when more F-15's could not be guaranteed, seemed logical.
Post the Invasion of Kuwait, US arms restrictions were lifted, probably for good.
But that was 5 years away in 1985.
Tornado F.3 gets a bad rap, but it's critics miss the point.
It was designed specifically for the UK AD
requirement, which included a major chunk of the Eastern Atlantic as well as UK airspace.
The targets would be bombers, Bears, Badgers, Bisons, Blinders, Backfires and SU
Endurance, ability to operate in all weathers in a heavy ECM environment, were important.
Here, a F-16 or even a F-18 would have fallen rather short, whatever their other virtues.
I doubt there were ever high hopes for Tornado F.3 exports, being so specific for the Cold War UK AD
mission, so the Saudi F.3 deal was a bonus.
But considering the Saudi requirement, it actually fitted in rather well.
Complementing the F-15's, which of course were proper dog-fighters, even if just allowing the Eagles to do their stuff while the F.3's maintained CAP's covering both gaps and a second line of defence.
That they have been withdrawn after 20 years of service is no great surprise.
Typhoons are coming, after all.