On 29 March 1946, eight-year-old Renata awoke on a ship entering the Pool of London. With her was Frederika, in her early thirties, a cousin by marriage. Awaiting them was Renata’s father, Erwin. Their last meeting had been on 1 September 1939, when Erwin had been called as a reserve medical officer to his Polish cavalry regiment. Renata was just 23 months old.

Renata’s mother, Tosia, had died in Auschwitz. Her grandparents, uncles and aunts, as well as cousins (including Frederika’s husband Frezio) and friends had all been murdered by the Nazis.

Frederika, a Jewish survivor, had protected Renata throughout the War. Renata was moved from place to place and deception to deception. She had hid under a table for hours as the Gestapo took away her little cousin and playmate and shot her in the street. She had borne the privations of a children’s home where she was fed mouse pie for lack of any other meat.

For Renata, London promised excitement and security. She barely knew what a father was, yet she idealised the security he would offer in a strange land. As the ship approached Tower Bridge, she saw it as a fairy tale castle, with her father-prince awaiting her. As they wept together on meeting, Renata, forced into early maturity by her experiences, said to him: “Hello Tatús. Here we are at last. This is Frederika. I think you know her. She is very nice and I think if you are planning to marry again you ought to marry her.”

Frederika had acquired a non-Jewish nom de guerre and by then was working as a secretary in the Polish Embassy in Oslo. She returned and love letters followed — on the phlegmatic Erwin’s side full of passion, from gregarious Frederika, full of caution for Renata’s welfare. Some months later, Frederika defected from Poland and married Erwin in Perth. They had one child. Thus it was that I entered this displaced family, with my sister Renata 10 years older than me and like a second mother.

Forward ten years. Renata was at university and I was becoming more curious. Our father was a GP in Lancashire. The marriage, formed out of tragedy, had succeeded despite my parents being temperamental opposites. Frederika had become Renata’s mother and I really thought  that this was the truth.

Our Jewish blood and background was never mentioned — I knew nothing of it. Renata had been told not to reveal anything to me. There was no domestic memorial to Tosia, not even a photograph. My mother had talked her way into a meeting with the Anglican Bishop of Manchester and the whole family became church attenders. I was baptised into the Church of England, was a choirboy for 11 years and was confirmed. Another bishop was a close family friend.

When I was ten and was told that Renata had once had “another mummy”, I was amazed even by the little of the story explained to me. It drew me even closer to my beloved sister. Yet even then, nothing was mentioned about our backgrounds. It was years later when that surfaced fully, when I was near to adulthood.

Renata has written and published the story of her years in Poland. Searing and compelling, it reminds us of the importance of the essence of our history. Renata had married the perfect Englishman who was patient with her anxious and dark feelings about the past. Today she suffers from severe dementia, which he and their daughters bear with huge courage. The last time I saw her in her nursing home, I only penetrated the confusion in her brain when she joined me in the songs she sang when I was little, and read her favourite poem, TS Eliot’s Macavity: the Mystery Cat, which she had taught me.

I doubt her diagnosis, at least in part. I believe that the unspeakable cruelty and persecution she suffered, the knowledge of her mother having been tortured and murdered, exacerbated her condition and advanced her symptoms.

Over the years we talked about our suppressed Judaism. We believe our parents made their decisions through fear of recurrent persecution. My mother always travelled with luggage to enable her to face another episode of living by her wits. We don’t blame them. As a family we have rediscovered, even created, a family record of Tosia’s own heroism and suffering. I regret that I did not experience being brought up as a Jew, and that I have so little knowledge of Judaism despite the support of good Jewish friends. It is a serious lacuna.

This month I have started as Chair of the Woolf Institute’s Commission on the Integration of Refugees. Perhaps the experience of Renata and me, as well as our parents, will find some passage there.

Lord Carlile is a crossbench peer. Renata’s childhood experience can be found in ‘Let Me Tell You a Story’, by Renata Calverley