The Honda rider fired in a lap of 2m05.004s early on to lead Yamaha's Maverick Vinales by seven tenths of a second.

The four-time COTA winner followed that up with a 2m04.622s, beating Vinales' FP1-topping effort of 2m04.923s by three tenths.

Vinales became the second rider to dip beneath the 2m05s barrier halfway through the session on his second run, setting a 2m04.945s.

The Yamaha rider subsequently closed on Marquez further as he improved to a 2m04.837s, before grabbing the top spot with a 2m04.451s with 18 minutes to go.

That stood as the benchmark until the dying stages of the 45-minute session, when Tech 3 Yamaha rider Johann Zarco used soft tyres front and rear to eclipse Vinales with a 2m04.347s.

Marquez, running a medium front and soft rear, was soon to deny the Frenchman however as he improved to a 2m04.061s on his final run, enough to beat Zarco by 0.286s.

Vinales didn't use a soft tyre at the end of the session and didn't improve, but his earlier time on medium tyres front and rear was enough for third, 0.390s slower than Marquez.

Valentino Rossi made it two works Yamahas in the top four, albeit 0.355s slower than teammate Vinales and 0.745s off the pace of Marquez.

Fifth was the second factory Honda of Dani Pedrosa, followed by Andrea Dovizioso on the best of the Ducatis and Cal Crutchlow's LCR Honda, while Folger on the second of the Tech 3 Yamahas was last of those to get within a second of Marquez.

Scott Redding (Pramac Ducati) and Andrea Iannone (Suzuki) completed the top 10, with Jorge Lorenzo on the second works Ducati just behind in 11th with a best time 1.221s off the pace.

The second Suzuki of Alex Rins suffered an engine blow-up on its first lap out of the pits, although the Spaniard was able to continue on his second bike to finish the session 18th.

KTM rider Pol Espargaro tried out a new aerodynamic winglet fairing on his way to the 20th-fastest time of the session, 2.442s behind Marquez.

Loris Baz (Avintia Ducati) and Karel Abraham (Aspar Ducati) both suffered crashes in the closing stages of the session, with the latter requiring a trip to the medical centre with a suspected ankle injury.

The Czech rider was later reported to have suffered a hairline fracture in his right ankle, and will require further checks before he is cleared to ride on Saturday.

Practice results:

Pos.	#	Rider	Bike	Time	Gap
1	93	Marc Marquez	Honda	2'04.061
2	5	Johann Zarco	Yamaha	2'04.347	0.286
3	25	Maverick Viñales	Yamaha	2'04.451	0.390
4	46	Valentino Rossi	Yamaha	2'04.806	0.745
5	26	Dani Pedrosa	Honda	2'04.811	0.750
6	4	Andrea Dovizioso	Ducati	2'04.830	0.769
7	35	Cal Crutchlow	Honda	2'05.005	0.944
8	94	Jonas Folger	Yamaha	2'05.033	0.972
9	45	Scott Redding	Ducati	2'05.116	1.055
10	29	Andrea Iannone	Suzuki	2'05.142	1.081
11	99	Jorge Lorenzo	Ducati	2'05.282	1.221
12	9	Danilo Petrucci	Ducati	2'05.284	1.223
13	43	Jack Miller	Honda	2'05.463	1.402
14	41	Aleix Espargaro	Aprilia	2'05.468	1.407
15	8	Hector Barbera	Ducati	2'05.584	1.523
16	19	Alvaro Bautista	Ducati	2'05.602	1.541
17	53	Tito Rabat	Honda	2'05.943	1.882
18	42	Alex Rins	Suzuki	2'06.155	2.094
19	76	Loris Baz	Ducati	2'06.358	2.297
20	44	Pol Espargaro	KTM	2'06.503	2.442
21	17	Karel Abraham	Ducati	2'06.709	2.648
22	22	Sam Lowes	Aprilia	2'06.741	2.680
23	38	Bradley Smith	KTM	2'07.434	3.373