On Vinogradov's mean value theorem: strongly diagonal behaviour via efficient congruencing

We enhance the efficient congruencing method for estimating Vinogradov's integral for moments of order 2s, with . In this way, we prove the main conjecture for such even moments when , showing that the moments exhibit strongly diagonal behaviour in this range. There are improvements also for larger values of s, these finding application to the asymptotic formula in Waring's problem.