As was the case at Mugello, for most today represent a step into the unknown, for while a couple of teams have tested here over the years and few drivers have raced here, this is the first time any of them have experienced the rollercoaster that is Portimao in contemporary machinery.
Ahead of today's opening session, the air temperature is 17.5 degrees C, while the track temperature is 22.3 degrees. It is bright and sunny. Nonetheless, there is a 10% chance of rain.
For the first time this year, there is a move away from the standard allocation of eight softs, three mediums and two hards. For this weekend, and in Turkey next month, the drivers will all be given seven sets of soft, three sets of medium, and three sets of hard. This is to cater for the expected severity of these two tracks.
The compounds on offer are the hardest in the range, the C1, C2 and C3.
The lights go green and Giovinazzi leads the way, followed by Vettel, Grosjean and Albon. Unfortunately, Giovinazzi goes off at Turn 1 as does Latifi.
Vettel posts the first time of the weekend (30.462), but this is soon eclipsed by Sainz (30.401).
Sainz improves to 24.452 but his time is immediately deleted for exceeding the track limits at Turn 4.
Next time around Sainz improves again, describing the track surface as "Tokyo Drift", but this time his time is deleted for going wide in Turn 1.
Kvyat is unhappy with his visor feeling that it is "too bright", which could be an issue on a track where one spends so much time looking at the sky.
As Verstappen posts a 25.682, Sainz posts a legitimate 22.183.
No sooner has Verstappen had a time deleted than the Red Bull star spins at Turn 4.
"Mate, this wing off-set is completely wrong," he complains.
Meanwhile, Sainz has got down to 20.696.
As Russell and Raikkonen post times, 19 minutes in both Mercedes finally appear, leaving Ricciardo as the only 'no show'.
Verstappen argues with his engineer over what actually constitutes the track limit.
Sainz remains quickest (20.696), ahead of Verstappen, Bottas, Russell, Albon, Gasly, Hamilton, Latifi and Vettel.
This is very much being used as a test session, not only for new components for with an eye on the remainder of the weekend and even 2021. Lots of aero rakes and flo-vis.
Despite the new track surface, the cars appears to be struggling for grip as they slide about.
Leclerc goes third with a 23.400, as Hamilton posts 22.090 and Bottas 21.713 to go second.
"There's no tyre grip, it's incredibly slippery," says Russell.
Ricciardo finally heads out and immediately goes 18th with a 27.231.
A 20.410 sees Leclerc go top, as Gasly goes third (20.908), ahead of Hamilton and Bottas. However, the world champion subsequently leapfrogs the Frenchman with a 20.883.
More and more drivers have their times deleted, with Turns 1 and 4 the scene of most of the crimes.
Gasly goes top with a 20.365, as Ricciardo improves to 14th with a 22.506.
A 20.165 sees Hamilton go top, as Leclerc spins at Turn 14 and is lucky not to end up in the gravel.
The Monegasque subsequently reclaims his top spot with a 20.130. That said, Hamilton responds with a 19.526.
At the 40 minute mark, when the drivers hand back a set of tyres, it's: Hamilton, Leclerc, Bottas, Sainz, Gasly, Vettel, Albon, Perez, Norris and Ricciardo. Verstappen is currently 20th, 3.692 off the pace having completed 10 laps.
So far, all the running has been on the hard tyre.
After several minutes of inactivity, Grosjean and Latifi head out to get proceedings underway again. While the Frenchman sticks with hards, the Canadian is on mediums.
As more drivers head out, a number are now sporting the yellow-banded mediums.
Russell heads out, his team having changed the floor on his car.
Perez goes second (19.907) on the mediums, ahead of Bottas, Sainz, Gasly and Vettel.
Kvyat says his tyres are not looking good after just 4 laps and he needs to cool them.
Drivers continue to have their times deleted, Turns 1 and 4 still the main cause of their problems.
Bottas goes top with a 19.491, with teammate (adversary?) Hamilton posting a 19.526 to go second, just 0.035s behind.
Replay shows the Finn suffer a mighty wobble exiting Turn 8.
"It's spitting a little bit," reports Norris, however he is told that there is nothing showing on the radar so it is not significant.
As Stroll warns of "someone dropping oil on the track", attention turns to the rear of Verstappen's Red Bull.
"Apparently blocking is not a problem," sighs Grosjean.
Hamilton posts an 18.874 to go top, while Verstappen improves to fourth with a 19.719.
Quickest in all three sectors, Bottas crosses the line at 18.410.
"Box, box, we have an issue on the car," Gasly is told.
Verstappen improves to third with a 19.252, while Albon goes sixth with a 19.729.
Perez is warned that the wins has picked up and that there's a 10 kph tailwind into Turn 3.
A spin for Raikkonen in Turn 5, one of the slowest corners - if not the slowest corner - on the track.
"Keep an eye on your front-left," Bottas is told, "other people have graining."
"Left graining," reports Hamilton as if by magic.
Very early days, but surprising to see the Renaults down in 18th and 19th.
At which point Ricciardo improves to 8th with a 20.058.
Stroll also in the lower reaches of the timesheet along with the usual suspects.
Giovinazzi improves to 16th with a 21.009. Teammate Raikkonen is currently 13th (20.280).
Kvyat spins at Turn 3, the Russian losing the rear of the AlphaTauri.
Leclerc complains about Bottas deliberately slowing down at various points on the track.
As smoke billows from the rear of Ocon's car, the session ends. The Frenchman is told to "box" and "not change gear".
Bottas is quickest, ahead of Hamilton, Verstappen, Leclerc, Albon, Sainz, Perez, Raikkonen, Ricciardo and Gasly.
Vettel is eleventh, ahead of Norris, Kvyat, Magnussen, Stroll, Giovinazzi, Grosjean, Russell, Ocon and Latifi.
Check out our Friday gallery from Portimao, here.