Found it! It is explained in Maureen Lipman's book "How Was It For You?"
The numbers of the days, weeks, months, years equal vowels. A=1, E=2, I=3, O=4 and U=5.
The intials of the place names are the consonants.
'And then' means a new word. You normally spell a clue rather than the name but I guess you could do either.
Examples...
One day in London and stayed three = Ali, as in Mohammed Ali the boxer.
Yugoslavia for 4 weeks and 5 days = You.
Quebec for five months 2 weeks 2 days Niagra and Seattle 'and then' Saratoga for 3 days and Seattle = Queen's Sis, ie Princess Margaret.
I hope that helps.
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Many a child has been spoiled because you can't spank a Grandma!