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"I am delighted to be elected and to have the mandate from RIBA members to undertake my election pledges on improving pride, fees and diversity within the architecture profession," said Duncan earlier today.
"Over the next year I will be working hard to support Stephen Hodder, and visiting and talking to members and staff across the UK."
The architect, who has run her 16-person practice since 1992, will become the 75th president in the institute's 180-year history, giving direction to RIBA policy and budget.
She will officially be given the title President Elect on 1 September 2014.