Beat the cream cheese, mayonnaise and horseradish in a small bowl with an electric mixer until creamy. Stir in the cheese, ham and pimientos. Shape the mixture into a log 20 cm long. Wrap the log in plastic wrap and refrigerate for at least 2 hours (it will keep for 2 days).
Spread the chives or spring onions on wax paper. Unwrap the log and carefully roll it in the chives or spring onions, until it is completely coated. Rewrap the log in plastic wrap and refrigerate until serving time.