Thanks drizzle. I changed the s3 part to .historyclass and I get the blue line down the right of the two columns, but I do not get it between the columns where there are two columns. I have experimented and can get the blue line on all sides of the one column!
The page is a trial at the moment at https://glio.me.uk/Trial/page-15/. For the date 5-Apr-1802 I want there to be a vertical line between the 5th & 6th April