Complex sentence: It passes through Mill Hill, separating with the A1 at "Apex Corner" roundabout After crossing the M1, near Elstree, it links the M1 at Junction 4, and then meets the A5 at a roundabout (where the A5 becomes the A5183).
Split into simpler sentences: It passes through Mill Hill, and separates with the A1 at a roundabout at "Apex Corner". Near Elstree, it links the M1 at Junction 4, then meets the A5 at a roundabout (where the A5 becomes the A5183).