IT was a cold December night last year when Margot Lack arrived home to what she thought was an ordinary letter on her doormat.

The letter explained a social worker in Leeds had been contacted by her sister, Pamela Archer, a stranger for 56 years.

Mrs Archer, of York, had been trying to make contact with her for the past three decades and had finally struck gold.

“When I opened the letter I thought it was from a charity,” recalls Ms Lack, 56, in the lounge of the Grand Hotel where she is meeting her sisters for the first time.

“I checked it again and saw my original birth name, thought ‘oh my God’ and realised this was about me. I was awake most of the night and had to phone in sick the next day.”

Ms Lack, a health care assistant, was adopted when she was weeks old in 1960, leaving behind her sisters Pamela and Wendy, and brother Christopher at their home in Derbyshire.

Pamela Archer, 63, is the eldest and has been trying to contact her sister for 33 years.

Until 2005 only a person who had been adopted could search for their relatives, leaving Mrs Archer without many avenues to explore. However, the law was relaxed 11 years ago and with the help of the internet and PAC UK - an organisation which searches for relatives - she was able to contact her sister and the family began swapping messages.

Mrs Archer, of Galtres Avenue, Heworth, with her husband, lost her mother last year shortly before she found her sister. She spent months arranging the meeting and sweating over the details of a poignant day.

She said: “It’s surreal. It’s how I planned it but the nerves have been huge. We never spoke about it in my family when my mum was alive, that’s just how it was.

“I asked her permission to search and she gave us her blessing, which spurred me on.”

Ms Lack was given up for adoption by her mother, a single parent who struggled financially, but said she had a wonderful childhood and had known from the age of 10 she was adopted and had siblings.

“It’s amazing,” she said.

“I always knew there were three others but I had an amazing upbringing and childhood.

“I never thought about meeting them because I was really happy.”

In fact, Mrs Archer and her younger sister had lived only three miles apart in Derbyshire and believe they may have crossed each other’s path in shops, restaurants and pubs many times.

Wendy, 59, who has one daughter, added: “We just couldn’t wait for the day that we found Margot. I will never forget the morning Pamela phoned me and said somebody had found her.

“It was the best Christmas present we could ever have.”