FP2 was 45 minutes old when it was red-flagged by Gasly's AlphaTauri bursting into flames at Portimão's Algarve International Circuit, leading to the Frenchman jumping hastily from his car before it was attended to by marshals who quickly extinguished the fire.
It resulted in a 16-minute delay but just five minutes later FIA race director Michael Masi was forced to issue a second red flag when Stroll and Verstappen collided at turn one.
Racing Point confirmed Stroll was on a second flying lap, while Verstappen had just started his, which resulted in neither giving way at the first corner.
With Stroll on the racing line, the Canadian turned in on Verstappen on his inside, sending the former into the gravel, while the Dutch driver was at least able to make his way back to the pits, but ultimately resulting in a stewards' investigation.
There was a further 16-minute hiatus before the session resumed again with just eight minutes remaining, leading to 18 drivers - minus Gasly and Stroll - heading back out, and with the majority on the soft tyre for this weekend.
At the conclusion of a captivating session, Bottas held sway, clean sweeping Friday for the third consecutive race - not including the recent Eifel GP when Friday was fogged off.
Bottas finished quickest with a lap of one minute 17.940secs, comfortably ahead of Verstappen by almost six-tenths of a second, but with the Red Bull driver's best lap on the medium compound.
It is the first time in 24 years Formula 1 has visited Portugal, and it is clear the track nicknamed 'the rollercoaster' given its undulating nature will prove to be a challenge across the remainder of the weekend.
With it being a new circuit, and in particular with newly laid asphalt and heavy rain earlier in the week to make it additionally 'greener' than might otherwise have been expected, across both sessions the drivers complained of low grip.
They were followed by Sebastian Vettel in his SF1000, and Gasly, even though he missed half the session, with both also on mediums.
The problem for all the teams and drivers was the fact it was a highly disrupted session, sparked by the fact the first half-hour was given over to Pirelli testing a range of 2021 prototype tyres, which resulted in a considerable amount of running from all the drivers.
Each team was provided with three sets, two for one driver and one for the other, with the driver with the one set under instructions to focus on a longer run.
There were complaints at times of graining, whilst Hamilton, in particular, bemoaned a severe vibration that restricted his vision to such an extent he was forced to box.
Whilst times were predominantly irrelevant, for the record Verstappen was quickest with a time of 1:21.57s, followed closely by Bottas. Williams' Nicholas Latifi was slowest, 2.7s back.
The Pirelli running basically led to an hour-long practice session for the teams to re-focus on set-up for the weekend.
But the two red flags and the loss of 32 minutes in total threw spanners into the works.
Behind Hamilton, he was followed by the Renault of Esteban Ocon and Red Bull's Alex Albon, the latter 10th and 1.703s down.
Williams' George Russell, one of the few drivers who managed to get in a flying lap before the mayhem started, was 11th quickest, 1.881s down.
GPFans is a multi-platform, multi-language brand dedicated to Formula One coverage. We bring you all the ins and outs of the sport, 24/7, everything from up-to-the-minute news and features to the latest viral stories and clips.
We believe that a new generation of exciting, outspoken drivers will make F1 more popular than ever before, and we want to give our users access to as much of their heroes as possible, on and off the track. From Lewis Hamilton to Max Verstappen, Daniel Ricciardo to Sebastian Vettel, we provide in-depth analysis of every every Grand Prix in the season, from Australia to Abu Dhabi.
With Formula One under the new ownership of Liberty Media, how the sport is being covered is evolving, and GPFans will look to be at the heart of this progression into new media, as one of the fastest-growing sites covering the king of motorsports.