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How to wire a trailing socket before you fit the flex

Updated: 23 October 2026

The box on the bench is a socket body and nothing else. Every Masterplug bar in our [extension lead without cable comparison](/hub/sockets-and-extension-leads/extension-lead-without-cable) arrives without a plug and without flex. How to wire a trailing socket comes down to flex size, a BS 1362 fuse in a BS 1363 plug, and whether you can tell the conductors apart. Peter F. used the amazon.co.uk listings plus Electrical Safety First and BEAMA. There was no lab test. A qualifying purchase can earn a commission at no extra cost to you. If the body is still an open choice, start with the [rewireable trailing socket buying guide](/hub/sockets-and-extension-leads/extension-lead-without-cable/sub/extension-lead-without-cable-buying-guide).

The box on the bench is a socket body and nothing else.

Our top picks

Masterplug Masterplug ELS13W-01

Best overall

Masterplug Masterplug ELS13W-01
9.8/10about £4.38
View offer
Masterplug Masterplug ELS132W-01

Alternative

Masterplug Masterplug ELS132W-01
9.6/10about £5.09
View offer
Masterplug Masterplug TN-MP

Best value

Masterplug Masterplug TN-MP
9.6/10about £3.84
View offer
On this page
  1. 1.Flex and fuse before you open the cover
  2. 2.Terminals, grip and cover
  3. 3.Checks before you energise
  4. 4.When not to wire it yourself

Flex and fuse before you open the cover

BEAMA's checklist sets a minimum cross-section, not a maximum length. Up to 2 metres, 1 mm² three-core is the floor. Past 2 metres, use 1.25 mm² or 1.5 mm². A 5 metre bench run is already past that step. Guides that name a flexible cord usually point at three-core H05VV-F. Two-core lamp flex has no earth, and these bars have an earth terminal because earthed tools need it. The fuse belongs in the plug: a 13 A BS 1362 fuse in a BS 1363 plug for a 13 A lead. A replaceable-fuse bullet on the socket does not retire that, and TN-MP reviews say the block itself has none. Regulation 35 of the Electrical Equipment (Safety) Regulations 2016 requires a correctly fitted standard plug and fuse on a domestic lead for a BS 1363 socket. A BS 1363-2 line on the body is not a certificate for the lead you assemble. Reuse an old kettle lead only if it is three-core, the sheath is intact, and the printed size meets the length rule. If the printing has worn off, do not guess the copper.

Terminals, grip and cover

Current UK flex uses brown for live, blue for neutral, and green-and-yellow for earth. In the plug, brown goes to the fuse terminal marked L, blue to N, and green-and-yellow to E. The trailing socket uses the same letters, but the screws may not copy the plug, so follow the marks in that body. The fuse stays in the plug. The cord grip clamps the outer sheath, not the coloured cores alone. If only the inner wires are trapped, a tug pulls on the terminals. Leave sheath under the clamp, keep every strand inside its terminal, and fit the cover before you go near a wall socket. If the grip will not close on the sheath, recut rather than forcing the screws.
Masterplug Masterplug ELS13W-01

Testsieger

Masterplug Masterplug ELS13W-01
9.8/10about £4.38
View offer

Checks before you energise

Thirteen amps is the total through the plug and the flex, not per outlet. A kettle around 3 kW already uses about that budget on 230 V, so a heater on the next gang is an overload. Electrical Safety First warns against daisy-chaining leads. Uncoil the flex before you load it. A tight coil can heat the way a wound cable reel does. With the plug top off, confirm the sheath is under the clamp, the cores match L, N and E, and the fuse is a 13 A BS 1362 link. Fit the socket cover, then insert the plug. Heat, a smell, or a breaker that opens at once means the lead stays out. Floor knocks and a damp shed sit on the trailing socket for a workshop page.

When not to wire it yourself

Stop if you cannot name brown, blue and green-and-yellow. Red and black are an older code. Do not translate them from memory. Stop if the earth is missing, the sheath is split, or the grip cannot hold the jacket. Tape is not a cord grip. This is a portable lead, not a new circuit or a fixed socket in the wall. Call an electrician if the fault is in the installation, or if the job has become fixed wiring outdoors. A finished lead is the alternative when you wanted length without opening a cover. Rockers are a separate choice on the switched or unswitched trailing socket page.

Common questions

What flex size should I use for a 5 metre bench lead?
Use three-core of 1.25 mm² or 1.5 mm². BEAMA's checklist allows 1 mm² only up to 2 metres, and 5 metres is past that. Read the size on the sheath. H05VV-F is the flexible type guides usually name. If the marking is gone, buy marked flex rather than guessing.
Do I need a 13 A fuse in the plug?
Yes. BEAMA pairs a 13 A lead with a 13 A BS 1362 fuse in the BS 1363 plug. A fuse mentioned on the socket, or a TN-MP review that says the block has none, does not remove it. A 3 A fuse is for a lighter cord and a small appliance, not for a bar you may load to 13 A.
Can I reuse an old kettle lead?
Only if it is three-core, the sheath is sound, and the printed size matches the length. A short 1 mm² lead can meet the under-2-metre rule, but heat cracks near the old kettle mean that piece should be scrapped. Two-core flex leaves the earth empty, so it does not feed this socket.
Where do brown, blue and green-yellow go?
Brown goes to L, on the plug the terminal beside the fuse. Blue goes to N. Green-and-yellow goes to E. Use those letters in the trailing socket as well, because the screws may not mirror the plug. If you find red and black, stop instead of guessing.
What is the cord grip for?
It holds the outer sheath so a pull does not rip the cores from the screws. It is not a clip for the coloured wires alone. Leave sheath under the clamp at both ends, held firmly without crushing the cores. If the clamp cannot close, change the flex or the plug rather than leaving the sheath outside.
When should I stop and call someone?
Stop before power if you cannot identify the cores, if the earth or sheath is damaged, or if the grip will not hold. Stop after power if the lead heats, smells, or trips as soon as you plug in, and leave it out. Fixed wiring, or a wall socket you no longer trust, needs an electrician.

Related pages

Extension lead comparison

Extension lead without cable

Best trailing socket without cable on amazon.co.uk

Rewireable trailing socket: what to check before you buy

Switched or unswitched trailing socket for a UK bar

Trailing socket for a workshop bench or a dry shed

Sources

Sources taken from the research digest. Listings were scored on 20 October 2026. This page did not run a lab test.

  1. Electrical Safety First — Extension leads (retrieved 20.10.2026)
  2. Electrical Safety First — Plugs and fuses (retrieved 20.10.2026)
  3. BEAMA — Extension lead safety checklist (retrieved 20.10.2026)
  4. Plugs and Sockets etc. (Safety) Regulations 1994 (retrieved 20.10.2026)
  5. Electrical Equipment (Safety) Regulations 2016, regulation 35 (retrieved 20.10.2026)
  6. Heathfield LED — Masterplug Permaplug ELS132B (retrieved 20.10.2026)
  7. amazon.co.uk — trailing socket listings (retrieved 20.10.2026)