I haven't made the change yet, as I see there have been some tagging disagreements previously, but Sundon Road from here to Lower Sundon should surely be Tertiary, as it's a moderately important road, the Central Bedfordshire C198, which then continues right along Sharpenhoe Road and Church Road to the A6.

By contrast, it's Sharpenhoe Road north of here and between Church Road and A6 which should be the minor road