Dear Mary: How can I spike a gossip-pedlar’s guns?

Q. On arrival at a top level dinner, I was surprised to see at the table a woman who, I have reason to suspect, sells gossip as a sideline. However, clearly no one else suspected her and, assuming it was Chatham House rules, everyone was talking freely. When one man began to regale the table with an anecdote which was bound to culminate in a dynamite piece of gossip, I was paralysed with horror but I couldn’t think how to stop him before it was too late. The consequence was that the item appeared in the press a couple of days later, causing all manner of probable future security problems to the subject of the story. Although I can’t prove it was this woman who sold or leaked the gossip, I strongly suspect she did. For various reasons I know it must have come directly from that dinner party since no one else, except the anecdotalist, knew the gossip.