The first time we opened the relationship

We had talked through the rules for weeks: limits, a safeword, hygiene and no pressure. She arrived on time in London, friendly and clear. We had a drink, the three of us kissed and we went upstairs. It started with touch between the two of us while he watched, then he joined in. The threesome was more tender than wild: turns, laughter, checks that everyone was still all right. We finished sweaty and pleased, without odd jealousy. We slept for a bit and had breakfast together. Opening the relationship was not chaos. It was conversation and adult sex, properly spoken. We will do it again when all three of us ask, and not before.