The bits people ask before they pick up the phone.

Optical fibre cable that hasn’t been lit yet — no carrier equipment on either end. You light it yourself with your own kit, at whatever bandwidth you want, for as long as the cable lasts. Most leased lines run over the same physical fibre; the difference is who owns the ends.

The maths usually favours dark fibre past 10Gbps of sustained traffic, or once a leased-line contract is heading past five years, or when you have multiple buildings to connect. We’ve seen cases where dark fibre pays back in year two. We’ve also seen cases where a leased line is still the right answer. We’ll tell you which one yours looks like — in writing — before you commit.

Probably not, if you’re a single small office. Probably yes, if you’re a data centre, an ISP with multiple sites, a university with a campus, or anyone who’s about to renew a leased-line contract for the third time and noticed the bill compounds. The answer’s commercial more than technical — it depends on bandwidth, contract length, and how many buildings.

You do, in most arrangements we recommend. Sometimes we structure it as an IRU (Indefeasible Right of Use) — a long lease that behaves commercially like ownership without the asset on your balance sheet. That can suit AI infrastructure and DC operators where the accounting matters. We walk through the options at the Consultancy stage.

Tell us the postcodes you want to connect and the bandwidths you’d want at each. We come back with a budgetary quote — same hour or same day for straightforward jobs, same week for the larger, more complex ones. The quote includes a written view of likely Excess Construction Charges and wayleave timings.

Carrier options for the route. Bandwidth options. Indicative kit. ECC ranges where we can estimate them. Wayleave assumptions. A timeline from order to live. Nothing branded as “from £X / mo” — the cost depends on your specific route, and we’d rather give you a real number than a marketing one.

Excess Construction Charges. The bit of a leased-line install that wasn’t in the original quote — usually civils work the carrier discovered when the surveyor turned up. Industry-wide, around 85% of quotes contain unlisted ECCs, typically £1,000 to £10,000. We try to estimate them before you sign. If we’re wrong, we wear it.

Permission from a landowner, council, or building owner to put a duct across or under their property. Wayleaves are the slowest part of most builds because they involve other people’s lawyers. We start the wayleave conversations in parallel with the design phase — usually weeks before they’d otherwise come up — so the build doesn’t stall when civils start.

Smaller than people expect, often. The Midlands DC survey was £100,000 in survey work that added many times that in resale value. Two-building corporate links sit at the small end. The 15-site AI DC evaluation sits at the larger end. We’ll quote whatever’s worth quoting.

UK-wide. We’ve delivered in West London, eleven cities for Ask4 (York, Bath, Southampton, Glasgow, Aberdeen, Lancaster, Falmouth, Sheffield, Nottingham, Cardiff, Birmingham), Heriot-Watt at Galashiels, GCRE in South Wales, Carbon-Z at Swindon, the Midlands DC, and the OFWAT Dark Fibre 2 project across multiple water-utility regions. Wherever Openreach and a couple of national carriers reach, we can usually pick a route.

Depends on civils and wayleaves, not on us. Surveys: same week. Designs: a few weeks for medium projects. Builds: anywhere from weeks (when the civils are short and the wayleaves are clean) to several months (when they’re not). The published industry average for a 1Gbps Openreach leased line is 60 to 120 working days. On the parts we control, we’re usually quicker — and you get a realistic timeline before you commit, not an optimistic one.

Yes. RADAR doesn’t need permission from anyone else — it can sit alongside your current maintainer’s contract, give you live fault location, and you keep calling your existing team to fix things. We’re often the layer underneath the maintenance contract, not the replacement for it.

You may own the fibre or have an exclusive-use lease but, either way, RADAR can be incorporated as part of your own service and doesn’t need permission from anyone else.

As part of the installation we map the fibres in your network to our inbuilt GIS system. We know the length of the fibre and plot key points in the route to build a fibre map.

That’s OK. RADAR uses detection waves in the 1650nm bandwidth which don’t affect the live data. We’ll just agree a planned maintenance window while we install a coupler on the live fibres in your data centres.

Yes, but now you can tell them exactly where the fault is and get it rectified quickly without SLA issues.

Owning — the fibre is yours, on your asset register, lit by your kit. You decide when to upgrade bandwidth or change equipment. Leasing — you rent the lit service from a carrier; they own the fibre and the kit. IRU (Indefeasible Right of Use) — a long-term lease, typically 15 to 25 years, that behaves commercially like ownership but stays as an off-balance-sheet contract.

Cost certainty over the contract life. The dark fibre asset has a long life — physical cable installed today will carry data for decades, with bandwidth changes coming from equipment upgrades, not contract renegotiation. The Ask4 case study puts it plainly: “Ownership of the fibre fixes the costs and provides a saving or 50% or more over the projected life of the contract.” That’s the live-site quote, not marketing copy.

No. Most of our owned-fibre clients run on a Sicom Support contract with RADAR-monitored care. You own the asset; we look after it. Civils teams for external repair, on-call engineers for fault location, reinstatement of the service once the cable’s back together.

Few competitors do business this way. Most carriers prefer the lease model because it produces recurring revenue. Our different business model — own your network — needs explaining and selling, and that’s part of the job. It’s also why we wrote this page.