addressing a mayor

We're having an event in school in May and are inviting the mayor of the town to it. I got the official protocol info for inviting the mayor to an event and am in the process of filling that out. I need to include a letter with more info for him so how do I address the letter? Dear who? Mayor? Mayor and surname etc?

Actually literally just back from a photo call with the Lord Mayor in Cork. When writing to his office I addressed him as Dear Lord Mayor of Cork. I called him Mayor when I met him until he asked me to call him by his first name. I think some are called titles but that's very dated and not so commonly used now.

Thanks. Will draft that letter now and run it by principal in morning.

I could be wrong but I think the Lord bit of Lord Mayor only applies to cities. Now, I don't know what I'm basing that on but I think it is. I THINK if it's Kildare County Council or a local town council like say Naas or Newbridge that he's just the 'Mayor' of the town. So I would say Dear Mayor O'Brien or Dear Mayor Tom O'Brien. Then on the day Mayor O'Brien or if he's an elected representative to the council (which he should be if he's Mayor) Councillor O'Brien. Actually probably best to stick to Mayor O'Brien if he's there in an official mayoral capacity. Hope that made sense!!

Cheers SK! Just googed his name and its on council site as Mayor. Now need to find the official titles for others we have to ask. Know one of 2 are councillors but not sure of others.