A colleague of mine has recently be suspended, pending a hearing, for phoning up sex chat-lines on the work phone and racking up a three figure phone bill. What I don't think my boss knows is that he regularly watches porn at work and doesn't even clear the internet history.

I have a lot to gain from this man being sacked, but he has a daughter to look after and I don't think I'm a bad person.

What I'm asking is, should I tell my boss about his other activities?

I could discretely send him and email so no-one else would know it was me who grassed him up, but I might have a hard time explaining to my boss why I didn't let him know about this sooner.