Click here for full BSB FP1 results from Silverstone
Jakub Smrz has become the surprise timesheet topper in an opening session hit by delays and rain which gave the majority of riders little opportunity to produce useful laps.
The Smiths BMW rider pinched top spot just as conditions were at the optimum before a red flag ended the session with just under seven minutes remaining, preventing any quick blasts before the chequered flag.
His top time was eight seconds off of the fastest lap set at the official BSB pre-season test from Leon Haslam last week and unlikely to be fully representative of the true pace of the BSB field.
John Hopkins on the all-new ePayMe Yamaha claimed second in the truncated session, ahead of Shane Byrne on the Be Wiser Ducati as James Ellison and Christian Iddon completed the top five.
BSB rookie Sam Hornsey claimed an impressive sixth on the new Team WD-40 Kawasaki ahead of Alastair Seeley, Peter Hickman, Luke Mossey and Jack Kennedy rounding out the top ten.
The opening practice session of the season had to be delayed by 95 minutes after an earlier incident in the British Supersport FP1 saw oil spilt at turn six which required an extensive clean-up programme. As a result, the session was trimmed by five minutes with warning flags for surface conditions at turn six and into turn seven.
Half the BSB field chose for early runs to test out conditions, which were already tricky due to overnight rain, with Byrne heading proceedings albeit over 10 seconds off the pace produced when the series visited the Northamptonshire track during pre-season testing.
As the shortened session entered the final 10 minutes Smrz nipped to the front on the Smiths BMW to prove conditions were improving all the time but the morning run was prematurely halted as rain began to fall at sectors one and two while Danny Buchan also suffered a technical problem with his Lloyds British Moto Rapido Ducati at Copse.