To me that was a secondary thing. Leclerc was driving to the pace that he felt would get his tyres to whatever lap Ferrari had decided to pit him on. It meant the cars were running at a pace several seconds slower than they are capable of, a pace that everyone can run at, and so it does get backed up. It means that an undercut F1 is trickier as you can get stuck into traffic. I think that’s why Vettel stopped on the lap he did. What he needed to do was to make sure he didn’t get stuck behind Hulkenberg, because Nico was running at quite a respectable speed. Hulkenberg was on the hard tyre so he wasn’t about to pit any time soon and the available gap was diminishing. So Ferrari had to pull the trigger then to get in front of Hulkenberg. I don’t believe they thought it would work as well as it did – I don’t think anyone did. But when you look at it, Vettel must take some of the credit, because his out lap was a second quicker than Leclerc did a lap later. There was a very good F1 undercut, Leclerc and Vettel did very similar lap times on their in lap but Vettel’s out lap sealed it.