As the previous post was short and to the point.I thought I would add this short anecdote...
A top sommelier in London was asked about the biggest faux pas he'd ever made.
'A table of 6 ordered a bottle of Petrus 1978( at £600). After the host's approval I started pouring for the other guests. Once the fifth glass was poured the bottle was finished. I said 'this one has run out, shall I bring another?'. The guest wasn't happy.'
The obvious solution would be for the other guests to each pour a drop into the 6th glass..but as my humour is well know..my reply would have been...'bring him a glass of the House Red!!'