Fortunate car drivers may be familiar with the “green wave”, in which a sequence of traffic lights are coordinated so that each conveniently turns to “go” just as the vehicle approaches. To judge by the first round of France’s parliamentary elections on Sunday, Emmanuel Macron seems to have invented the green wave’s political equivalent.

In the 10 months since he launched his meteoric political career, Mr Macron’s radical centrist project has found every traffic light of the many that might have blocked his path on green. If next week’s second round confirms Sunday’s results, the French president and his new party will have secured an overwhelming parliamentary mandate for his reform agenda. Theresa May, who will sit next to Mr Macron at the Stade de France on Tuesday evening for a football match, can only look on with drooling envy.

At the start of this year, Mr Macron’s fledgling party La République en Marche did not even exist. Now it is projected to win between 400 and 450 seats out of the 577 in France’s national assembly. In Sunday’s first round, La REM finished first in the majority of seats and came far ahead of its nearest rival in terms of national share of the vote. This sweeping success is one of the largest in the history of the Fifth Republic. Yet it has been achieved not by one of the well established parties or blocs but by a new movement, half of whose candidates had never stood for public office before. In some respects this is an even more formidable achievement of mobilisation than Mr Macron’s success a month ago.

It is significant that more than half of French voters failed to go to the polls on Sunday. Turnout was a mere 49%, compared with 78% for the first round of the presidential election at the end of April. Yet this high rate of abstention needs to be interpreted with care. The Fifth Republic’s constitution has always elevated the president above the parliament. National wariness about political “cohabitation” – a president and parliament of competing parties – tends to be reflected in higher abstention on the opposition side, as on Sunday. And the French electorate may be suffering voter fatigue after a succession of primaries and presidential votes in recent months. To that extent, low turnout may not be as damaging in practice to Mr Macron and La REM as the numbers may imply.

For the moment, however, it is Mr Macron’s political opponents who are in disarray. France seems to be witnessing a process of dégagisme – of clearing out old parties and leaders. The left is deflated after the worst Socialist result in parliamentary elections since François Mitterrand refounded the party at the Épinay congress in 1971. The centre-right is deeply divided. Meanwhile the hard right Front National, which lost 4 million votes on Sunday compared with Marine Le Pen’s showing in the first round in April, now faces a gruelling internal conflict over its political direction, a battle that is likely to come to a head at its party conference in 2018.

Mr Macron is on course to win a decisive mandate. This is important not just for France itself but for the European Union. Germany’s willingness to help loosen the eurozone’s fiscal strictness will inevitably have to await the Bundestag elections in September. Yet Berlin will be under little pressure to act unless Mr Macron is seen to be credible as a reformer of France’s high-spending, high-unemployment economy. That depended upon the results in these elections. Signs of improving economic growth are yet another well-timed green light for Mr Macron.

The fact remains that three out of four French voters did not vote for Mr Macron in the first round in the presidential contest, while two out of three of those voting on Sunday did not support La REM either. This will certainly not prevent Mr Macron from getting his public spending plans and his labour market liberalisation proposals through parliament later this year. He will face challenges, perhaps including demonstrations and strikes, from the unions (with whom he has promised to consult over the summer) which will test the resolve and discipline of his tyro legislators. Plans to incorporate emergency anti-terror powers into the criminal code after the welcome ending of France’s 14-month state of emergency provide a further point of conflict. One day, Mr Macron will be faced with a red light. Seen from across the Channel, however, France’s quiet revolution of the centre appears an extraordinary and, in many ways enviable, contrast to the snarl-up in Britain.