HMLR Local Land Charges programme

Not strictly a PDTF "adoption" story, but a parallel public-sector programme with the same shape: standardise the data, run a national register, drive local-authority migration. PDTF's llc1.json overlay aligns directly to the HMLR LLC schema.

What the programme does

Local Land Charges (LLC) are statutory entries against a property — restrictions, notices, listing designations — historically maintained by each local authority in their own format and accessed via paper or fee-bearing search products (LLC1 form). HMLR's national programme:

• Standardises the data model for LLC entries
• Provides the central digital register
• Migrates each council's existing data into the standard format
• Maintains the register going forward with a quality assurance regime ("gold status")

How it relates to PDTF

The PDTF overlay llc1.json is shaped to match what the HMLR LLC search returns. A PDTF-compliant search consumer can therefore use HMLR's API directly as the upstream source, with the same field names, types and enumerations.

Conceptually this is one of the cleanest upstream-as-source-of-truth patterns in the framework: HMLR runs the system, PDTF consumes it, no separate standards body in the middle.

OPDA video coverage

OPDA's YouTube channel includes three HMLR-LLC explainer videos:

• Creating a national Local Land Charges Register (1:05)
• Local land charges: How the Data Analysis Dashboard tool works (5:15)
• Maintain LLC register (6:25)

All three in source/05-engagement/videos-youtube/embedded/.

Significance for the wider programme

HMLR's LLC programme is the public-sector pattern OPDA's Sandbox approach is intentionally mirroring: pick one use case, standardise the schema, build the central infrastructure, drive migration with quality gates. The LLC programme is roughly five years ahead of OPDA on that curve, which is why DPMSG cites it as a reference precedent in the Spring 2025 Interoperability Report.