The first designated bathing water area on the River Thames in London will welcome swimmers for the official start of the bathing season on Friday as one of 13 new monitored swimming areas across England. The Thames at Ham, in south-west London , has been designated as a new river bathing water area after campaigners gathered evidence to show thousands of people use the river for swimming throughout the year. Marlene Lawrence, the founder of the Teddington Bluetits, which has more than 2,000 members, put in the bathing water application alongside her colleagues. “This is amazing for the river and for the many people who enjoy it,” she said.…