Dear Mary: How can I stop predatory kisses at social gatherings?

Q. How can one politely stop predatory kissers? I am (or was) an affectionate and demonstrative person but I don’t wish to immediately go back to kissing and hugging — even close friends — at social events, let alone people I have just met. I accepted an invitation to my first (garden) lunch since lockdown because I was told we would be only six.