Mercedes driver Valtteri Bottas set a time of 1m27.629 to lead the majority of the session, although light rains limited the race in the last half hour and skewed the order.
Lewis Hamilton finished a double in Mercedes, but was replaced late by the Red Bulls of Pierre Gasly and Max Verstappen.
Gasly then improved on his last run to clock a time of 1m27.173 and a lead of almost half a second in front.
The start of the session was marked by a series of laps as the drivers became familiar with the newly redesigned Silverstone circuit, starting with Romain Grosjean crushing his Haas out of the pitlane.
Grosjean lost the back of his car when the pit lane exit flew to the right and he broke his front fender against the barrier before rolling briefly in the wrong direction to find space for turn around.
After that, British GP rookies George Russell and Lando Norris had their turn.
The Williams pilot, Russell, was found in the grass after being shaken by the left-handed Brooklands and spit in the opposite direction.
Norris was left the wrong way in the second lap of the home straight at the start of the McLaren, after losing the back after the last corner.
The session was then stopped, with Raikkonen's Alfa Romeo being found after a full break at the entrance to Luffield.
Replays showed a puff of smoke coming from the back of the Raikkonen Alfa that was slowly circling Brooklands as the car appeared to have stuttered and then cut the Wellington Straight.
Once the session resumed, Hamilton, Bottas and Alex Albon had more or less serious moments through Brooklands and, in the same corner, Grosjean completed a difficult session by performing another rotation.
Light rain began to fall as the last half-hour approached, sending most cars into the pit lane, although McLaren's Carlos Sainz stayed on track.
The drizzle never turned into heavy rain and stopped early enough for some drivers to improve the last minutes of the session.
Nobody made the rounds quickly enough to drop Bottas at the start, but Gasly came close to a time of 1m27.715 which propelled him to second place.
When the checkered flag fell, Gasly completed a new lap in soft tires, which allowed him to take a step ahead.
Verstappen was third, 0.8 seconds slower than his team-mate, and Hamilton fourth.
A late improvement by Charles Leclerc was enough for fifth gear, one second of speed and just ahead of teammate Sebastian Vettel.
Nico Hulkenberg and Daniel Ricciardo gave a boost to Renault after the poor GP of Austria finishing 1 st and 7 th and 1 st. Albon and Sainz complete the top 10.
Results of the session