Over-wing pylons on Jaguar.

Dear all,
Antbody know the reason why some(not sure if its all) RAF Jaguars have over-wing pylons fitted, why not under like ‘normal’. A few of the reasons I can think of:

1.Lack of space under the wing.

2.A problem with balance of the aircraft.

3.Cheeper. Knowing the MoD the reason was that it cost less! hehe

Any thoughts?

Cheers, ARKID.