Monaco F1 track drain covers strengthened after Button incident

First practice was red-flagged after a drain cover on the exit of Ste Devote worked its way loose, puncturing Nico Rosberg's left rear tyre and hitting the front-right corner of Jenson Button's McLaren.

Button praised the work officials do on the circuit but said the incident should not have happened while his team-mate Fernando Alonso said it strengthened the case for improving cockpit protection.

FIA race director Charlie Whiting inspected the scene after the incident and it was welded back into place.

It has since emerged the drain cover was a square inspection hatch measuring around 25cm x 25cm that cracked and came loose.

All covers had been checked, fixed and welded in four places but evidently this was not sufficient as when the hatch broke, the welds were not big enough to retain it.

As a result, all the vulnerable covers were inspected and welded down around a larger part of their circumference ahead of support race running on Friday.