N°4 lies behind a low sandstone arch off Crooms Hill, in the lee of the Royal Observatory. The arch is the original 1820 — listed, kept, restored stone by stone — and the planning brief required everything beyond it to be visibly of its own time.

6a's response is a long, low brick volume that follows the historic stable line on plan but does nothing else to mimic it. The brick is handmade in Suffolk, laid in a soft running bond with lime mortar; the roof is a folded zinc plane that lifts at the rear to draw north light into the kitchen. Inside, the principal volume runs the full length of the plot under a single 30-foot oak lining — floor, walls, ceiling — pierced by a top-lit stair to the mezzanine bedrooms above.

The garden is the work of Dan Pearson Studio: a 30-foot walled space planted as a single-season meadow, re-cut every February