Question for those who know about Chiltern + Wembley. We will be taking the train from Marlyebone to Wembley for a Chelsea/Liverpool match.

1) Chiltern has added a bunch of trains that day (trains running about 10 minutes apart before/after game). In terms of buying tickets, even though I'm able to select specific times, do those operate as a first come/first served model, or is my ticket guaranteeing the specific train?

2) Anyone have a clue how early to arrive at the stadium? I don't need to be there for a ton of waiting time, so just curious as to the expected time from train arrival @ Wembley to being in my seat, with the various queues and COVID vaccination checks? I am thinking to arrive about an hour before the match.

Thanks in advance.