Unofficial practice day - always Thursday rather than Friday here in the Principality - has the capacity to produce meaningless scenarios and the contest proper begins with tomorrow's qualifying session.
However, Herbert's elevation to the top of the Formula One practice charts for the first time after a century of races is a significant gauge of the progress he and the Sauber-Petronas have made in tandem.
Certainly there was nothing half-baked in the endeavours of Michael Schumacher and Jacques Villeneuve, the two drivers closest to the Englishman. And try suggesting to Heinz-Harald Frentzen, winner of the San Marino Grand Prix a fortnight ago, that his commitment was diminished. He crashed his Williams-Renault into a barrier in vain pursuit of Herbert's time.
Herbert's current driving is like his natural demeanour: a joy to encounter. He professes himself at home with Sauber; comfortable and appreciated. And, he says, the traumas of his life and career have insulated him against the pressures of F1.
Herbert explained: "I had to get over my accident in 1988 and then difficult times at Lotus and Benetton. There's a lot more mental warfare in F1 these days and I've survived it because I'm tougher now. Going through all I went through has helped me cope with today's F1, where you often find drivers head-to-head and criticising each other. We had it with Michael Schumacher and Damon Hill.
"I've not got myself involved in that sort of thing and I'm happier now than I have been for three or four years. I'm with a team where everyone is working to the same end."
Herbert, a resident of Monaco, is usually to be seen on these streets travelling within the legal speed limit of 25mph at the wheel of his jeep or astride his Harley-Davidson. Local knowledge may well have helped yesterday, but at 180mph the familiar landmarks mean little.
He said: "Silverstone is still my real home track, but it is nice and special when you do well here. Everyone wants to win at Monaco. It's a great challenge, perhaps the greatest challenge of all."
Damon Hill's objective this weekend is to finish a race for the first time in the Arrows-Yamaha. So far the champion's tale has been one of frustration, leading to speculation about his future. After taking ninth place yesterday, he sought to put the record straight on his supposed threat to quit the team unless they "get their act together".
He said: "I've made no threats, merely a statement of fact. I'm telling the situation as it is. We have had problems and the team know they have to be fixed. A huge amount needs to come if we are to be competitive by the middle of the season. I've got an open mind as far as next season is concerned, but at the moment I'm concentrating my efforts on Arrows."
MONACO GRAND PRIX: Free practice (2.093-miles): 1 J Herbert (GB) Sauber- Petronas 1min 21.188sec, 92.76mph; 2 M Schumacher (Ger) Ferrari 1:21.330; 3 J Villeneuve (Can) Williams-Renault 1:21.445; 4 G Fisichella (It) Jordan- Peugeot 1:21.463; 5 G Berger (Aut) Benetton-Renault 1:21.573; 6 M Hakkinen (Fin) McLaren-Mercedes 1:21.675; 7 H-H Frentzen (Ger) Williams-Renault 1:21.885; 8 R Schumacher (Ger) Jordan-Peugeot 1:21.939; 9 D Hill (GB) Arrows-Yamaha 1:21.962; 10 J Alesi (Fr) Benetton-Renault 1:22.010; 11 D Coulthard (GB) McLaren-Mercedes 1:22.020; 12 E Irvine (N Irl) Ferrari 1:22. 072; 13 R Barrichello (Bra) Stewart-Ford 1:22.370; 14 N Larini (It) Sauber-Petronas 1:22.383; 15 P Diniz (Bra) Arrows-Yamaha 1:22.622; 16 J Verstappen (Neth) Tyrrell-Ford 1:23.056; 17 O Panis (Fr) Prost-Mugen- Honda 1:23.096; 18 M Salo (Fin) Tyrrell-Ford 1:23.483; 19 J Magnussen (Den) Stewart-Ford 1:23.810; 20 J Trulli (It) Minardi-Hart 1:25.178; 21 S Nakano (Japan) Prost-Mugen-Honda 1:25.530; 22 U Katayama (Japan) Minardi- Hart, 1:39.353.Reuse content