What the letters on the dial actually meant

Before 1927 a London caller lifted the receiver and asked an operator for a name and a number. The General Post Office began installing the automatic Director system that year, starting with HOLborn at midnight on 12 November 1927, followed within six weeks by BIShopsgate and SLOane, then WEStern and MONument. There were around eighty manual exchanges in London when the programme began.

Under the Director system a London number consisted of the first three letters of the exchange name followed by four digits, and the dial converted the letters to figures. EUSton 1234 was dialled 387 1234; Wimbledon's WIM was 946. The point was memorability: a number carried its own address. Anyone reading PRImrose 4141 on a shopfront or a letterhead knew roughly where the shop was, in a way that no modern number conveys.

The exchange on Townshend Road

The equipment that served Primrose Hill sits at 41–43 Townshend Road, a substantial building that appears to date from the 1930s, when the GPO put up a number of large exchanges across London. It has always served both Primrose Hill and St John's Wood.

That address is itself instructive. Townshend Road is NW8, while most of the Primrose Hill streets it served are NW1 or NW3. Telephone exchange areas were drawn around cable runs and equipment capacity, not around postal districts, so the boundaries never quite matched. A household on the eastern slope of the hill and a household half a mile away in St John's Wood could be on the same exchange while sitting in different postal districts — and, as it happened, on different exchange names.

PRImrose and JUNiper

The Townshend Road exchange carried two names. The GPO's booklet Dialling Instructions and Call Charges, London, 1968 — issued immediately before the letters were withdrawn — lists both, and records the area served for PRImrose as St John's Wood, with Primrose Hill noted alongside it.

That difference mattered locally. Most London subscribers, when the names went, simply learned to write down digits they had already been dialling for years: JUNiper 2345 became 586 2345 and nothing else changed. PRImrose subscribers were not so lucky. Their code moved from 774 to 722, so a Primrose Hill number in 1969 was genuinely a different number from the one printed on the previous year's stationery.

The neighbouring codes fill in the local map. EUSton was 387, unchanged at conversion. GULliver, serving Kentish Town, was 485 and likewise unchanged.

1966 to 1970: the names withdrawn

All-figure numbering was introduced across the United Kingdom from 1966, with the changeover running until about 1970 and a public campaign — ANN: All-Figure Numbers Now — marking the end of parallel working. The Post Office had three arguments. London was running out of usable three-letter combinations. Telephone dials in other countries mapped letters to digits differently, so foreign callers dialling a London name reached the wrong number. And call routing into the major cities needed reorganising in a way the letter system obstructed.

The change was unpopular enough to be debated in Parliament. Objectors complained that all-figure numbers were harder to remember, that they came too soon after the upheaval of subscriber trunk dialling, and — the point that has aged best — that a number no longer told you anything about where it was. An exchange name had been a small piece of local identity, printed on vans, shop fascias, invoices and the enamel plates of tradesmen. PRImrose meant this hill; GULliver meant Kentish Town. Seven digits meant nothing at all.

What survives inside an 020 number

The digits themselves proved more durable than the names. London's code was split and renumbered several times after 1968 — the old 01 prefix gave way to 071, then to 0171, and finally to the present 020 7 — but the exchange codes underneath were carried forward each time.

The result is that the Townshend Road exchange still issues numbers in the 020 7722, 020 7586 and 020 7483 ranges, alongside some inner London numbers. The 7586 block is JUNiper, unaltered since the Director era. The 7722 block is what PRImrose became in the late 1960s. Anyone in NW1 with a landline beginning 7722 is dialling, without knowing it, a code assigned to this corner of London when the letters came off the dial — and the last surviving trace of a time when a phone number was also an address.