With weather and track conditions improving after earlier rain, the Moto2 riders were the only class able to get in slick-tyre laps during their second practice session at Silverstone on Friday.
But the patchy conditions meant the tyre change only paid off in the final five minutes.
It was then that Randy Krummenacher beat the best wet-tyre lap of Marc Marquez. The race-winning rookie then fought back after also making the switch to slicks to finish the session just 0.117sec behind Krummenacher.
Third fastest and best of the Brits this afternoon was Tech 3's Bradley Smith, 1.651sec from Krummenacher, with Dominquez Aegerter fourth for Technomag-CIP.
Krummenacher's Kalex team-mate and world championship leader Stefan Bradl only rode for three laps, at the end of the session, which was all he needed to be fifth fastest.
Bradl had been second quickest to home rider Scott Redding in the dry morning session. Marc VDS rider Redding was 23rd in the afternoon after missing the chance to try slicks, but remained quickest on combined times.
Friday practice (2) - Silverstone:
1. Krummenacher (Kalex) 2m 15.090s
2. Marquez (Suter) +0.117s
3. Smith (Tech 3) +1.651s
4. Aegerter (Suter) +3.042s
5. Bradl (Kalex) +3.109s
6. P. Espargaro (FTR) +3.842s
7. Pirro (Moriwaki) +4.156s
8. Pons (Pons Kalex) +4.158s
9. de Rosa (FTR) +4.509s
10. Y. Hernandez (FTR) +4.884s
23. Redding (Suter) +9.069s
31. Coghlan (FTR) +10.681s