Cullen drew level with table-topper Ryan McLeish on 16 wins for the year following Irish Stryker success the previous week, but a lower average number of starters for those victories left him third.
However, after prevailing in a close Lotus Cortina scrap with his son Victor and Pete Chambers in the Historic Racing Drivers Club's Allstars series at Silverstone, that class win has now sent Cullen Sr to the top of the table.
With only a small number of circuit racing events remaining in the rest of the year, his rivals have a limited window to prevent Cullen from finishing 2023 at the head of the rankings.
Further down the table, there are only a few changes after last weekend's action and two of these come courtesy of Ginetta GT Academy drivers.
Ravi Ramyead won two of the Donington Park contests - pouncing on an error from rival Nick White, who had in turn just grabbed the lead to take the second of those victories. Ramyead has therefore moved from 21st to ninth on the leaderboard.
However, a win in race three ensured White took the title and also means he gains five positions to move into 15th.
Steven Larkham took another Roadsports win at the Kirkistown season finale to jump from joint 40th to 29th. But his uncle Jim topped the opening race in another Radical PR6 to prevent the younger Larkham from rising further.
Source: Autosport