500N,
the criticism of 5X from 3X and the amphibious group within the RN was based on two issues - that the Bn's of 5X were unfit for operations, they were untrained in amphibious warfare and both the Bn's and the Bde HQ never got their heads around either the concepts or the threats, and that they were ill-equipped (vs those in 3X including the two PARA Bn's) for the conditions - and that whereas 3X was, from day one, a fighting, all-arms brigade with an established, coherant concept of operations, 5X was, in effect, an administrative formation with no all-arms or logistic 'heart' and no plan of what the hell it was going to do when it got there.
it was described at the time - perhaps harshly - as 1200 posh blokes who couldn't carry their kit and who didn't have any artillery, logistics, engineers, helicopters, or reece.