While Britain and America were engrossed in the pageantry and diplomacy of a US presidential visit last week, another event pretty much went unnoticed in most Western capitals - and it could have a profound impact on geopolitics.

The "Strategic Mutual Defence Agreement" was signed by Saudi Crown Prince Mohammed bin Salman and Pakistan Prime Minister Shehbaz Sharif on 17 September.

Seen as an "Islamic NATO" in the making, at its core is the clause that "any aggression against either country, shall be considered an aggression against both".

Article 5 of NATO states the same, and is the cornerstone principle of collective defence that binds members of the alliance.

If an ally is attacked, each member will consider it an attack against them all and will take action to help. This cl

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