SILVERSTONE, England, July 10 (Reuters) - Lewis Hamilton won his home British Grand Prix for the third year in a row on Sunday with Mercedes team mate and title rival Nico Rosberg finishing second but under a stewards' investigation.

The triple Formula One world champion's fourth home win, from pole position, was the 47th victory of Hamilton's career and cut Rosberg's overall lead to four points after 10 of 21 races.

Rosberg was slowed by a gearbox problem with five laps remaining and crossed the line 6.9 seconds behind and with a question mark over his result after Mercedes seemingly broke the rules on radio advice by telling him to avoid seventh gear.

Red Bull's Dutch teenager Max Verstappen was third, 1.3 seconds behind Rosberg, in a race that started behind the safety car after heavy rain.

(Reporting by Alan Baldwin, editing by Ken Ferris) ((alan.baldwin@thomsonreuters.com; +442075427933; Reuters Messaging: Reuters Messaging: alan.baldwin.reuters.com@thomsonreuters.net))