War is no child's play, and while one might overlook the search for a pretext, the mobilization of troops and the collection of strategic materials are indispensable.
Do not be fooled by Egypt's weakness; it all depends on whom you compare it to. At least on the African continent, it still holds sway, claiming to be the strongest nation in Africa.
Their biggest competitor is Ethiopia, but the British had helped to weaken this adversary. By the time they finished with Ethiopia, it was done for.
Make no mistake, the great powers still care about their prestige. Unless it was a small fry like Afghanistan, for the sake of pride, the British would have to cripple Ethiopia.
A hegemon needs to maintain itself by force. It's acceptable to lose to a European power of equal standing, but not to African natives.