For a while, I’d tried to feel angry with Dad for what he’d done, but I couldn’t get beyond the anger that I already felt for his part in what had happened to Mum. In that context, the mere sin of being married to both women at the same time seemed neither here nor there. I was angry with Grace for a bit, too, but that hadn’t lasted long. Grace had also been economical with the truth, but she’d kept Dad’s secrets with the best possible motives and, looking back, if she’d been honest with me at the time I might well have just followed Mum over that cliff. It wasn’t fair of me to be angry with her and it was also unsustainable, so that had to be abandoned.

And what about Clio? Clio was the best thing to come out of all this. Nothing about her or her attitude to me changed in the aftermath. And now she was my sister as well as my best friend. No wonder the two of us seemed to understand each other so well. We shared 50 per cent of our DNA! And we never allowed any of the double-dad crap to get in the way.

She rang me that first night after it had all come out, and we’d spoken every day since. She was determined not to let anything spoil our relationship and so far, it seemed to be working.

‘Did you get Mum’s card?’ she asked when she rang the day after it had arrived.

‘Yup,’ I replied non-committally. I’d been waiting for her to mention the invitation, but I wasn’t sure how I was going to deal with it.

‘So?’ she said in her bouncy puppy kind of voice. ‘Will you come? Please say you will. It’ll be so lovely to have you and the children with us. You have no idea how tedious it is to get through a Christmas dinner with Hector. He just seems to suck the fun out of everything these days.’

Well, that was hardly surprising. I’d had no further dealings with him since the meeting on the beach and I had no desire to either, let alone at Christmas.

Clio must have gathered my reluctance from my hesitation. ‘Oh, please!’ she begged, but in that second I knew I wasn’t going to change my mind.

‘I’m sorry, Clio,’ I said firmly, ‘but we like Christmas our way, with just the three of us. The kids’ll get cross if I start messing with the Allen family traditions.’

It was maybe a little cruel to put it like that, but it was true. We might be sisters but we weren’t part of the same family.