WSR's Andy Priaulx and MG's Andrew Jordan topped the two Saturday practice sessions for BTCC's sixth round at Snetterton.
Title contender Jason Plato seemed all but set to top at least one of the runs, but was dethroned in the dying moments on both occasions.
In session one, Plato had headed most of the morning session, but came up 0.055s short as Priaulx improved the benchmark as the chequered flag fell.
With the leaders lapping in the high-1m56s range, Honda's Matt Neal made up a very close top three, ending up less than a tenth off the leader. Plato's BMR teammate Aron Smith was fourth, while Jack Goff's MG completed the top five.
Smith led practice two as it approached halfway, when a red flag for Mercedes driver Aiden Moffat's off at Montreal brought on a lengthy stoppage. Moffat showed "signs of concussion" and was taken to hospital for checks.
As the session finally restarted, improvements were few and far between, until Plato stepped up to take over the first spot with six minutes left on the clock, his new benchmark also beating Priaulx's lap from the morning.
But Jordan drastically improved with mere seconds on the clock remaining and cleared the BTCC veteran.
Reigning champion Colin Turkington then also passed teammate Plato, the top three eventually separated by just 0.04s. Smith and Priaulx settled for completing the top five.
Mat Jackson, heading Motorbase's return to BTCC, was an impressive sixth in the first session, but could only finish as high as 16th in the second run.
Points leader Gordon Shedden was seventh and 12th respectively.