The theory also assumes, without any proof, that the day of Creation was the same length as it is now.If we go by what the Bible says, then the time from creation to today is approximately 6 thousand years.
London City Airport is the closest, approximately 6 miles from the city centre.
So Londoners could cross the Thames river. The present London Bridge was opened in 1973 and it replaced the previous one which was built in 1820. That older bridge was dismantled and has now been re-assembled in Lake Havasu City in Arizona as a tourist attraction.