Substitute Kai Havertz's late header took Arsenal to the top of the Premier League with a dramatic win at Brentford.In Mikel Arteta's 200th game in charge of the Gunners, Havertz's 89th-minute goal rescued a largely forgettable display in west London.After Manchester City and Liverpool drew earlier on Saturday, this win moves the Gunners one point clear at the summit.Arsenal's Leandro Trossard had a goal ruled out in the first half by the video assistant referee (VAR) but defeat was harsh on Brentford who were only denied goals of their own by exceptional clearances off the line from Declan Rice and Oleksandr Zinchenko.