Political commentator Iain Dale has told Daybreak that marriage "is a very conservative principle."
"David Cameron should be congratulated for providing the lead on gay marriages," he added.
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Prince Harry will move down to sixth in line to the throne.
Ongoing problems with the bank's online platform have seen customers make a raft of complaints.
The Duchess of Cambridge has been driven to St Mary's Hospital in London in the "early stages of labour", Kensington Palace has said.