How good is McLaren's car?
F1 teams use computers and mountains of data to assess the relative performance of their cars and engines.
Taking the engine performance out of the equation, McLaren believe their chassis is contending with Red Bull for second best on the grid behind Mercedes.
That sounds outlandish judging by the time gap between the cars - Alonso was 1.981 seconds off Lewis Hamilton's pole lap at the Spanish Grand Prix - but the evidence suggests they may well be right.
Engineers say the Circuit de Barcelona-Catalunya is one of the most effective all-round tests of an F1 car's capabilities.
The third sector of the lap is particularly good for separating out the chassis performance from that of the engine as it is predominantly slow and medium-speed corners with a comparatively small number of straights.
In that sector, Alonso was slower only than the Mercedes and Red Bull drivers in qualifying in Spain.