The Coastguard had its busiest day for more than four years yesterday after thousands of sun worshippers flocked to the coast.Soaring temperatures were recorded on Friday as it became the third hottest day ever in the UK reaching 37.8 degrees in London.But local authorities have warned beaches have become “unmanageable” due to large swathes of visitors, prompting fears around keeping people safe in the water.Many calls to the maritime agency on July 31 were about people being cut off by the