WATCH: Bottas forced to retire from second place after pit stop disaster in Monaco

Mercedes were already having an unusually tricky Grand Prix weekend in Monaco - but it got a lot worse during the race when Valtteri Bottas was forced to retire after a disastrous pit stop for the Silver Arrows.

Lewis Hamilton was unhappy with his car throughout practice and qualifying, eventually only able to take seventh on the grid, while Bottas was much quicker and lined up third for the Grand Prix - which effectively became second after polesitter Charles Leclerc was ruled out before the start with mechanical issues on his Ferrari.

Bottas was running a comfortable second behind race leader Max Verstappen when he pulled in for his pit stop on Lap 31. But it was immediately clear there was a problem as the right front wheel refused to come off the car.

WATCH: Heartbreak for polesitter Leclerc as he is ruled out of the Monaco GP before the start

The mechanics battled with the reluctant wheel but it simply would not come off, and Bottas had no choice but to climb out of the car and retire from the race. Mercedes later confirmed that the wheel nut had machined onto the axle, preventing them from changing the wheel.

The issue promoted Ferrari's Carlos Sainz and McLaren's Lando Norris into the podium positions, with Hamilton still running down in seventh.