Query for cleaning up the history records except the last one for each item

The query below will delete all the history records for each item, except one latest record

DELETE FROM Table1
WHERE itemHistoryId NOT IN 
(SELECT t1.itemHistoryId
 FROM Table1 as t1
WHERE t1.historyDateTime = (SELECT MAX(historyDateTime) FROM Table1 WHERE ItemID=t1.ItemID)) 

The subquery

SELECT t1.itemHistoryId
 FROM Table1 as t1
WHERE t1.historyDateTime = (SELECT MAX(historyDateTime) FROM Table1 WHERE ItemID=t1.ItemID)

will return all the records with the latest history date, one per each itemID (i.e. records to be kept), and the main query will pull all the records that are not included in this subquery and delete them