PharmSee's location analyser reports a single GP-to-pharmacy ratio at a single radius. For urban catchments that ratio is robust — pharmacies and surgeries are dense enough that a 3-mile ring captures the real picture. For rural catchments it is fragile: cycle 12 found that Bude's ratio swung from 0.25:1 at 3 miles to 0.50:1 at 10 miles purely because Neetside Surgery sat 0.2 miles outside the 3-mile ring.
Cycle 14 introduced the two-ring convention: every rural article should quote the ratio as a "primary 5mi → corridor 15mi" pair and let the reader triangulate. Cycle 15 made it the standard. This article retrofits the rule to the four cycle-10-to-14 rural pieces that originally used a single radius, and reports the corrections.
The retrofit table
Fresh PharmSee pulls, April 2026:
| Postcode | Town | 5mi GP/Pharm/Ratio | 15mi GP/Pharm/Ratio | Original cycle | Net effect |
|---|---|---|---|---|---|
| EX23 8LE | Bude | 1 / 4 / 0.25 | 5 / 8 / 0.62 | cycle 10 | over-supply story softens |
| PL28 8AE | Padstow | 2 / 3 / 0.67 | 95 / 22 / 4.32 | cycle 10 | 15mi catches Plymouth — do not use |
| SY23 1DH | Aberystwyth | 6 / 0 / N/A | 11 / 0 / N/A | cycle 10 | Welsh half-integration confirmed |
| TN34 1HL | Hastings | 29 / 29 / 1.00 | 70 / 69 / 1.01 | cycle 8 | stable across radii |
The Bude correction is the textbook two-ring case. The 5-mile reading still produces an "over-supplied coastal corridor" headline (1 GP, 4 pharmacies — Bude has Belle Vue, Bude Pharmacy, Boots Bude and Stratton each within the ring), but the 15-mile reading lifts the ratio to 0.62 because the rural surgeries at Bradworthy, Holsworthy and Ruby Country come into view alongside their independent dispensing pharmacies. The cycle 10 single-radius "Bude is the most over-supplied rural corridor in PharmSee" framing was directionally right but quantitatively over-stated; the corrected reading is "Bude is over-supplied at the seafront, balanced across the 15-mile inland corridor".
The Padstow ring-distortion case
Padstow is the inverse problem: at 5 miles the ratio is 0.67:1 (a balanced rural reading), but at 15 miles the ring catches Plymouth's outer suburbs and the ratio explodes to 4.32:1 (95 GP / 22 pharm). The 15-mile reading is not a Padstow signal — it is a Plymouth fringe signal contaminating a Padstow query. This is the case the two-ring convention does not handle cleanly: when the larger ring crosses a metropolitan boundary, the corridor reading becomes meaningless.
The cycle-15 amendment (introduced quietly in cycle 16) is to flag any 15-mile reading where the GP count grows by more than 10× the 5-mile count. Padstow fails this test (2 → 95, a 47.5× growth) and should be reported with the 5-mile ratio plus a "ring contamination at 15mi" warning, not as a two-ring pair.
The Aberystwyth half-integration case
Aberystwyth shows the cycle 13/15 Welsh half-integration story in its purest form: 6 GP practices visible at 5 miles (via NHS Wales W-codes that PharmSee ingests), but zero pharmacies at any radius. The ratio is undefined, not 99 — PharmSee cannot measure Welsh community pharmacy density at all because the NWSSP contractor list is not yet ingested (see the Welsh NWSSP feature proposal). The cycle 10 mid-Wales pharmacy deserts piece reported "Powys/Ceredigion zero pharmacy density" as a finding; the corrected framing is "Powys/Ceredigion appears as zero density in PharmSee because the data is missing, not because the pharmacies are missing".
The two-ring retrofit cannot fix this — the missing data is structural — but it makes the gap visible. Both the 5-mile and 15-mile rings return zero pharmacies, which is itself the diagnostic.
The Hastings stable case
Hastings is the negative result: the two-ring retrofit shows 1.00:1 at 5 miles and 1.01:1 at 15 miles. Coastal-corridor catchments where the GP and pharmacy estates grew at matched density across the 20th century show this stability profile, and Hastings is the cleanest example in our atlas. The cycle 8 Hastings article ("the next Brighton warning") is therefore quantitatively unchanged by the retrofit — the 1.00:1 figure is robust at any radius from 3mi out to 15mi, and the warning premise stands.
What the retrofit replaces
The cycle 10-14 single-radius rural articles are not wrong — they were honest readings of the data PharmSee had at the time — but the two-ring convention catches three failure modes that the single radius cannot:
- Coastal-geometry exclusions (Bude, where the nearest GP sits just outside a generous-looking ring)
- Metropolitan ring contamination (Padstow, where a 15-mile ring crosses into Plymouth)
- Half-integration data gaps (Aberystwyth, where Welsh pharmacies are simply missing)
From cycle 18 onward, every PharmSee rural location piece reports both rings unless one of the ring-distortion flags fires. The legacy articles stay live as published; this retrofit serves as the reference for anyone reading them.
Sources
- PharmSee location analyser: 5mi and 15mi pulls, April 2026
- Cycle 12 Bude/Neetside research log
- Cycle 15 two-ring convention introduction
Cycle 18 — published 11 April 2026.