Sorry if it wasn't clear. It was due to being out on the razz. No excuses for that at all. It was a stupid thing to do and i'm not defending it in the slightest. My original opinion was that dismissal was a little harsh IF it was a first time issue and the previous 5 months had been problem free. Especially for someone fairly young, who might turn into a productive member of the team for many years to come.
My advice at the moment has been to try and beg and ask for a second chance, even to suggest extending the original probationary period for another 3 months to prove his worth/reliability.
For some more info, the company involved is a fairly small (i think) Third Party IT Support type company, maybe around 5-10 employees. The person in question is my stepson so i accept i can't be fully impartial, although i do my best to take everything into account and believe i question things i don't know (such as whether there have been other incidents he's not told us about)