Possible Clues:

• Local visitor's smartest togs, as observed by Spooner
• One invited to the pub
• Newcomer to pub said to have hazarded what a body was on
• This is sure bet, eg to get drunk
• Spooner's Sunday clothes? Not what would normally be seen in the pub
• Pub's irregular offering
• Not a regular local porter?
• Spooner's most suitable clothing for a change of draught?
• What gives customers a bitter experience for a while?
• Not a pint of the usual in Spooner's Sunday suit?