Led flash for alert not working?

[fatboy]

I've upgraded to ios5 but can't get the led flash to work with alerts, can anyone give me any tips to get it working please? I had no problems with anything else for the update apart from this.

 

[renlopez]

I've upgraded to ios5 but can't get the led flash to work with alerts, can anyone give me any tips to get it working please? I had no problems with anything else for the update apart from this.

LED alerts seem only to work when the phone is on the lock screen.