The use of banned substances under medical prescription is a vexed backdrop to the whole doping issue in cycling, and it was put in the spotlight yesterday, ironically on the stage which the French sports minister, Marie-George Buffet, chose for her third visit to the Tour.

Mme Buffet is behind the doping crackdown which led to the Festina scandal of 1998, and has visited the Tour each year since, as if to reassure the venerable, creaking institution that there are no hard feelings.

Doping is not merely about performance enhancement, it is also about victims, and yesterday's was Jonathan Vaughters, a bespectacled, eccentric American climber who rides for Chris Boardman's old team, Credit Agricole.

He turned up at the start in Pau yesterday with the right side of his face swollen out of all recognition and only able to see out of one eye after an allergic reaction to a bee sting.

The anti-inflammatory he needed to cure the problem rapidly contains corticosteroids, which are banned, but can be used locally under prescription. Vaughters, who has been talking since Dunkirk of his determination to get through his third Tour, needed a general, not a local, injection. Doctors from the International Cycling Union are present on the race to decide cases of this kind: Vaughters was refused.

He quit the race as soon as the peloton sped up, to the frustration of his manager, Roger Legeay: "This is the perfect example of a therapeutic need, which is nothing to do with doping or performance enhancement. With a cortico-steroid treatment it would have been sorted in hours."

Vaughters abandoned because if he had taken the medicine he needed he would have tested positive, which may well be another first for the Tour.

To underline the irony of his situation, yesterday France's national anti-doping body, the Council for Fighting and Preventing Doping (CPLD), revealed that use of corticosteroids under prescription is still widespread in the Tour: half the 16 urine samples carried out over the weekend in the Tour contained traces of corticosteroids used under prescription, said the council's president, Michel Boyen, who feels this is too high.

The undercurrents may have been contradictory but yesterday's backdrop was deepest France at its simplest and best: fields of sweetcorn and sunflowers, stone-built fortified villages or bastides early on; red-brick hamlets with vast castles and churches as the finish approached, and everywhere avenues of limetrees to keep off the sun.

In the Toulouse hinterland at Labarthe-sur-Leze, vast posters greeted the regionals of the stage: the green-jerseyed Stuart O'Grady and his team-mate Chris Jenner, who have made the town their adopted home; the finish, 30 miles from Laurent Jalabert's home of Mazamet, belonged to the mountains leader and his brother Nicolas.

In 1999 the phrase "the American quarter-of-an-hour" was coined. It refers to the margin Lance Armstrong's US Postal Service team lets a breakaway gain before they begin to make the pace on the front of the peloton to prevent matters getting out of hand. Yesterday it was the "American quarter-century" as the Postmen allowed 25 of their fellows the mandatory 15 minutes, and the blond Belgian Rik Verbrugghe gave his team, sponsored by the country's national lottery, their first stage win since 1992.

Rik is almost as resonant a name in Belgium as Eddy, as in Merckx: the name was shared by two of the country's greatest cyclists of the 1960s, Van Steenbergen and Van Looy, dubbed Rik the First and Rik the Second.

Rik the Third is not in their league - both were double world champions - but this year he has been the country's star performer, winning the Criterium International stage race in March, the Fleche Wallonne Classic in April, and in May taking the prologue time trial in the Giro d'Italia at a record speed approaching 35 m.p.h.

Yesterday's was a convincing victory: solid graft in the breakaway group followed by a solo chase of a lone breakaway from the breakaway, the Italian Marco Pinotti. Verbrugghe's sprint win with his erstwhile companions breathing down the pair's necks was clinical, apart from the little matter of his sunglasses sliding down his nose not once but twice as he headed for the line.

Today the Tour heads north through the Dordogne, to the fiefdom of Bernadette Chirac, and the profile in the final 40 miles is uncomfortably hilly. If Lance Armstrong's lead were below 90 seconds it would be the perfect setting for an offensive by Jan Ullrich, but one word sums up the Texan at the moment: presidential.