Fresh from his victory in the Italian Grand Prix two weekends ago, Lewis Hamilton secured first advantage at this weekend's Singapore Grand Prix on Friday when he topped the times for Mercedes ahead of Fernando Alonso of Ferrari at the end of second free practice.
In a session interrupted by a red flag stoppage after Pastor Maldonado crashed into the barriers in his Lotus, Hamilton was comfortably the fastest driver with a clear advantage ahead of the two-time champion Spaniard and with team-mate and championship leader Nico Rosberg down in 13th.
Rosberg's session was damaged when he had to abort his fastest laps following Maldonado's spectacular mid-session accident at the exit of Turn 10, where the Venezuelan destroyed the right front end of his car.
Maldonado's spectacular shunt, on a day when the drivers experienced a partial ban on radio communications for the first time, ruined the German's bid to clock a fast lap.
It also left him suffering the first psychological setback in this weekend's episode of his duel with Hamilton for the title.
Australian Daniel Ricciardo was third fastest in the leading Red Bull ahead of Kimi Raikkonen in the second Ferrari, the Italian team enjoying a fillip in form after a desultory weekend at Monza two weeks ago while they are gripped by a major managerial shake-up.
Defending four time champion Sebastian Vettel wound up fifth fastest in the second Red Bull after only joining the fray with 12 minutes remaining following an engine failure at the end of his morning free session.
Kevin Magnussen was sixth ahead of his more senior McLaren team-mate Jenson Button with Sergio Perez and his Force India team-mate Nico Hulkenberg. Russian Daniil Kvyat was 10th for Toro Rosso.
Two weekends after their fine showing at the Italian Grand Prix the Williams men of Felipe Massa and Valtteri Bottas were down in 17th and 18th, but running with heavy fuel loads.
Earlier in the day, Alonso ended Mercedes domination of opening practice when he topped the times for Ferrari -- the first time in seven races that any car other than a Mercedes had lapped quickest in the first action of the day.
Vettel is hunting his fourth consecutive victory under floodlights on the streets of Singapore, but realised the severity of his problems in the morning when he climbed from his car and said: "OK, I think I have an engine failure."
For Vettel it may also mean he is forced to exceed the limit of five engines in a season, by taking a sixth Renault power unit and with it a 10-place grid penalty, though the team may choose to do that at another race.
On the first day of the modified ban on radio communications between teams and drivers, there were several amusing moments as drivers either stopped their engineers from talking or sought information that was banned.
In one, during the morning, Hamilton asked his race engineer: "What sector times are other people doing? Are they doing any extra laps?"
The engineer, aware that such information is not allowed to be broadcast, replied: "OK Lewis, we'll just continue with our programme -- and discuss this when we get back in the garage."
In the afternoon, it was Rosberg's turn.
Frustrated, he asked the Mercedes team: "Are you allowed to tell me my team-mate's lap times?"
He received a similarly negative response on a day that saw Hamilton enjoy fortunes running his way.
The sport's ruling body, the FIA had eased back from a total radio clampdown overnight because they did not want to unfairly hurt some teams more than others.
FIA Race Director Charlie Whiting said: "It became clear that some teams would be at a serious disadvantage compared to others -- not just in their knowhow or ability to react in the short term, but also with hardware choices that were made a year ago.
"Two types of dashboard were available to the teams, and one can show a great deal more than the other.
"So in the interest of fairness we felt it would be better to introduce it in two stages and that is what we have done now."