There is a perfectly good alternative to Spin-off 12 - to follow NCN 12 from the end of Ayot Greenway Arc 12 outer via Codicote, Knebworth and Stevenage New Town with its network of segregated bike paths under roundabouts all the way to the station. But... this rural ride from St Alban's via Ayot St Lawrence provides some of the best on-road cycling that Cycle Orbital has to offer: exceptionally quiet relaxed riding throughout on mostly good surfaces.
The ride starts on Arc 12 inner 0.3, then joins Spoke 12 through Oakland College grounds 2, but diverges E on Oaklands lane 2.8, then NE on Coopers Green Lane 3 - both unclassified but busy unrestricted roads. Thereafter, starting at Symondshyde Lane 4.5 it is quiet lanes all the way, apart from a brief off-road section (heavy going in wet conditions) as you cross Arc 12 outer Ayot Greenway 7.8 E of Wheathampstead. On the way you will have passed on Beech Hyde Lane, unseen as nothing remains above ground, Cassivellaunus’ HQ Oppidum 7.1.
The lanes resume after the brief off-road section 8.2 to Ayot St Lawrence - home to GB Shaw Shaw's Corner (NT) 9.5 and the famous Brocket Inn. The church is a picturesque ruin. After the inn, L through imposing gates - but you are on a public bridleway which becomes metalled for the descent to the River Mimram. L on Kimpton Road 10.7 briefly, then R at Kimpton Mill 11 for a short climb back up.
The unremittingly pretty countryside continues, but the vistas open up more, and the lanes are better surfaced as you climb imperceptibly to 140m at Easthall 14.4 - as high as these final miles of the Chiltern Hills reach.
Stevenage emerges below you to the east - but it lies beyond the A1(M). This is an impervious barrier to motor traffic (ironically), and it took some time to recce a route through that was cycle-able. A number of possibilities were investigated; this is the very pleasant winner!
Descend to Langley, cross the B656 Hitchin to London Road 15.5, pass through the hamlet and pick up a bridlepath 15.8. Soon there is a shortcut through the field but carry straight on through a delightful coppice. You have descended to Ippollitts Brook: this is one of the southernmost sources of water bound north for the River Great Ouse, draining into the Wash. Not that this sluggish surface water gets very far, for it disappears into sinkholes under a huge scrapyard after a mile or so, reappearing with more confidence south of Hitchin.
Now you will hear the A1(M), impenetrable western boundary to the New Town. Into the stranded hamlet of Norton Green on the far side, and there is an underpass 17.1; conundrum solved. The town is served by a large network of segregated cycle paths which you immediately join for the short traffic-free trip to Stevenage.