Необходимо воткнуть артикль a/an/the заместо точек. Начало не знаю правильно или

Необходимо воткнуть артикль a/an/the вместо точек. Начало не знаю верно либо нет. Если можно, сделайте заключительнее предложение с разъясненьем.
The Romans invaded Britain in AD 43 and,chasing ancient Britons along the Thames they came to the first place where it was easy to Cross. They built a garrison there -and London was born.
They also erected ... bridge over ... river. ... garrison became ... major trading post. Later, ... bridge suffered neglect and ... whole area was raided by ... Vikings. In AD 886 Alfred ... Great drove out ... Raiders, ... bridge was repaired and ... city prospered again. ... hundred years later, ... Vikings returned but King Ethelred sailed up ... Thames, attached ropes to London Bridge, headed downriver and pulled it down.