If anyone was still wondering whether Arsenal are truly back to their best, this win at West Ham will surely banish any lingering doubts.For the second time in a week, the Gunners put five goals past their opponents and this time they did it all in the first half.It made for a scintillating opening 45 minutes, which also saw West Ham score twice. Not since 2012 has a Premier League match had seven first-half goals, with only three previous examples in total.The second half was the opposite of the first. Not a single goal was scored and instead this game meandered to a quiet finish. Not that Mikel Arteta will have minded, with Arsenal hosting Manchester United on Wednesday night.This trip to West Ham was all about Arsenal securing the win that closed the gap to Premier League leaders Liverpool to six points. The Gunners can now sit back and watch Sunday’s showdown between the Reds and Manchester City in comfort.