Tribunals and lawyers will sometimes refer to a ‘Judge sitting alone’. This means that he is sitting without the lay-members. This is common in case management discussions and pre-hearing reviews.
What it doesn’t mean is that the judge will sit alone in the sense that nobody else will be there. If you’re a party or representing a party, you still need to go.
Of course, sometimes the tribunal will meet without the parties, usually to discuss their decision. This is called a ‘hearing in chambers’. Another similar bit of jargon is a hearing ‘in private’, which means that the tribunal, parties and representatives attend, but the public may not.
Like a lot of jargon, this is fairly obvious to lawyers. Non-lawyers may wrongly conclude that the words mean what they seem to mean, and not what lawyers have decided that they mean. If you are ever unsure, ask.