Kyle Edmund saw off Davis Cup team-mate Dan Evans in straight sets in the first round of the Monte Carlo Masters.
Edmund, ranked one place below Evans at 45 in the world, recovered from a slow start to win 7-5 6-1.
The 22-year-old from Yorkshire, who rates clay as his favourite surface, will play nine-time Monte Carlo champion Rafael Nadal in round two.
Andy Murray, who watched compatriots Edmund and Evans from courtside, plays his opening match on Wednesday.
The world number one will take on Luxembourg's Gilles Muller or Tommy Robredo of Spain.
Edmund and Evans were Davis Cup team-mates in Britain's quarter-final defeat by France earlier this month, but were pitted against each other for the first time on the ATP Tour in Monte Carlo.
The surface made the big-hitting Edmund a heavy favourite against Evans, who has just two main draw wins to his name on the surface.
However, Edmund opened with two double faults and looked nervous, slipping 4-1 down as Evans capitalised on the errors.
The 26-year-old from Birmingham could not maintain his advantage though, with Edmund fighting back to claim the set with the seventh break of serve in 12 games.
Edmund had to save break points again at the start of the second but, despite some wayward smashes, went on to dominate, sealing it with an ace after one hour and 20 minutes.