On receiving birthday congratulations from the Queen, they said they were honoured but neither could believe they had reached 100.
The identical twins, who travelled the world together in their youth, marked the occasion with a garden party at a retirement home in Eccles, Greater Manchester.
They joked with staff and fellow residents as they tucked into strawberries and cream to the sound of a New Orleans big band.
The sisters, who never married, say the secret of a long life is happiness and togetherness.
Speeding ticket
The pair have not lost their sense of adventure. Alice got a speeding ticket at the age of 91 with Nellie beside her as "co-pilot" and they only moved out of their own home eight weeks ago.
On receiving birthday congratulations from the Queen, they said they were honoured but neither could believe they had reached 100.
When asked where they worked Nellie joked: "On our hands and knees." But in reality the twins lived a privileged life.
They were two of three daughters of successful Manchester wholesaler William Clarke and his wife Adelaide.
They had no need to work but chose to run a dress shop and volunteered to be ambulance drivers in World War II.
They cruised the Mediterranean at the height of the Depression but promised never to fly until hooks were invented to hold up the aeroplanes.
Record breakers
The retirement home's nurse manager Geraldine Lythgoe said the pair were great fun to be with.
"They have a very dry sense of humour. They are very dignified and both have their own personalities - they are marvellous," she said.
"They have had a great life. Once Nellie had a date with someone she didn't really like so Alice went instead and kept up the pretence for the whole evening."
Alice and Nellie cared for their parents until they died and outlived their younger sister Queenie.
Their birthday has earned them a place in the Book of Guinness World Records as the UK's oldest living twins.
A spokeswoman for the publication said the chances of identical twins reaching 100 were one in 700 million.