Fernando Alonso led a Ferrari one-two at the end of first practice for this weekend's Spanish Grand Prix.
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The conditions at Barcelona's Circuit de Catalunya, however, meant Alonso's time was five seconds slower than the best from testing at this track in early March.
Steady rain fell prior to the start of the 90-minute session, turning to drizzle in the early stages, forcing the intermediate tyres to be used for those who bothered to venture out.
The rain eventually relented to offer up a dry-ish line late on and allow the teams to switch to the hard tyre, resulting in considerable improvement in the closing stages.
But for every team such conditions meant the raft of updates on their cars this weekend - as is traditionally the case when the racing returns to Europe - could not be properly put through their paces.
That was especially the case for McLaren, with the most to gain given their appalling start to the year.
Requiring as much time as possible on track to get a handle on their new parts, frustratingly Jenson Button and Sergio Perez spent the majority of the time in the warmth of the team's motorhome.
Perez did not set a time until the dying moments and finished 13th overall, with Button failing to trouble the timesheet with any of his six laps to prop up the standings.
Overall, the duo completed just 12 laps between them, whereas every other driver was at least in double figures on the lap charts.
On home soil, and as he did last year, Alonso topped FP1 with a lap of one minute 25.252secs, finishing two tenths of a second clear of team-mate Felipe Massa.
To put that time into perspective, come the conclusion to the eight days of testing at this track in late February and early March, Nico Rosberg in his Mercedes was quickest with a 1:20.130secs.
Toro Rosso's Jean-Eric Vergne finished closest to the Ferraris, just over four tenths of a second down, followed by Romain Grosjean in his Lotus and Force India's Adrian Sutil, both within a second of Alonso.
Beyond that, Mercedes' Lewis Hamilton was sixth on the timesheet, 1.122secs adrift, and with his best lap blocked by a Red Bull and a Williams.
Completing the top 10 were Valtteri Bottas in his Williams, Lotus' Kimi Raikkonen, Rosberg and Paul Di Resta in his Force India, the Scot 1.5secs down.
As for the Red Bulls of Sebastian Vettel and Mark Webber, they were down in 19th and 20th, further underlining the nature of the poor weather, with both men 4.2secs off the pace.
For the first time in FP1 this year there was no Max Chilton, with the Briton making way for Marussia reserve Rodolfo Gonzalez who was 21st and the slowest of those who set a time, finishing over five seconds back.