Complex sentence: As of March 2014 there were an estimated 1,553 million round £1 coins in circulation, of which the Royal Mint estimated in 2014 that 3.04% (i.e. about 47 million) were counterfeit.
Split into simpler sentences: As of March 2014 there were an estimated 1,553 million round £1 coins in circulation. The Royal Mint estimated in 2014 that 3.04% (i.e. about 47 million) were counterfeit.