Leading 2-0 after the first leg at the San Siro and on a seven-match winning run, Inter were well-fancied to complete the job and they could well have done so in the opening 45 minutes, as Edin Dzeko forced Mike Maignan into a brilliant save before the break.
Milan had one big early chance themselves, Brahim Diaz wasting his opportunity when completely free in the box, but they were incredibly poor on the whole and even at two-goals down on aggregate the task felt beyond them.
That was confirmed with 15 minutes remaining, when Romelu Lukaku found space to slide Martinez in and the Argentinian lashed a low strike beyond Maignan, ending any hope the Rossoneri had of a late charge and ensuring Inter’s focus could turn to the final in Istanbul on June 10 as they eased to a 3-0 aggregate win. It will be their first Champions League final appearance since lifting the trophy in 2010.
Rafael Leao returned from injury to boost Milan’s hopes of an unlikely comeback, but he struggled to get on the ball in the first-half and when he did, the Portuguese star looked well off the pace. His one bright moment came when shrugging Matteo Darmian off the ball and driving into the box, but the shot was dragged wide of the far post.
Milan’s biggest chance came before that though, during a brief spell in which they at least raised the possibility that the tie was not yet over. Sandro Tonali burst away superbly down the left and cut the ball back for Diaz, who went for placement rather than pace and instead found neither as Andre Onana kept the effort out.
Inter were a real threat on the break, Henrikh Mkhitaryan going close on more than one occasion from distance before Dzeko’s flicked header was somehow kept out by Maignan, that reflex save just about keeping his side in the tie despite a goalless first-half.
It left Milan needing two goals after the break - they managed just a single shot in the 45 minutes that followed. Olivier Giroud headed wide and that was as good as it got for them, a succession of poor crosses sent into the Inter box the extent of the attacking threat.
Any trouble to the scoreboard increasingly looked like coming from Inter and so it proved, ending Milan’s race once and for all. There was little space for Lukaku in the box but he managed to squeeze a pass through to Martinez, and this time Maignan was beaten as the shot flew past him at the near post. This was a sensational night for Inter, though a far more difficult one awaits next month against either Manchester City or Real Madrid.