Scope and Content

These plans comprise the largest known collection of plans of the Flintshire and Denbighshire lead mines. They relate mainly to mining carried out from the various drainage tunnels driven to underwater mines in Holywell, Halkyn and Mold.

Administrative / Biographical History

In 1818 Earl Grosvenor started a level from Nant-y-Flint at a height of 180 ft 0D to drain water from the Halkyn mines. It was continued intermittently thereafter. In 1875 an Act of Parliament empowered the Halkyn District Mines Drainage Co to levy royalties on mines in the area drained by the level. Begun in a south-westerly direction, this level (known as the Halkyn Deep Level, Halkyn Tunnel, Old Drainage or 1875 Tunnel) was driven southwards, eventually (in 1901) reaching the South Llyn-y-pandy Mine, nearly five miles from the portal.

A second tunnel was begun in 1897 at sea level near Bagillt. This tunnel (known as the Milwr Tunnel or Sea-Level Tunnel) was driven by the Holywell-Halkyn Mining & Tunnel Co, which had been empowered by an Act of 1896 to drain mines north of the Halkyn District Mines Drainage Co area. In 1913 the latter company obtained an Act of Parliament to extend the Milwr Tunnel into their drainage area, whose boundary, beneath the hamlet of Windmill, on Halkyn Mountain, was reached in 1919. Halkyn District United Mines, formed in 1928, continued driving the tunnel and mining veins accessible from it throughout the 1930s, when up to 650 men were employed. In 1938 the low price of lead forced the laying-off of most of the workforce. No mining was done in the war years, when large quantities of TNT were stored for the Ministry of Supply in specially-constructed stores underground. In 1948 work on driving the Milwr Tunnel was restarted. This continued until 1957, when the tunnel reached the Cathole Vein, near the Mold-Ruthin road, over ten miles from the portal. It had been intended to drive the tunnel into the mines to the south, in the Maeshafn-Llanarmon area of Denbighshire, but this plan was abandoned and mineral leases in this area were given up in 1960.

In the post-war years lead ore was mined at intervals up to 1977, but much work was done mining high-grade limestone for Pilkingtons, the glass manufacturers, and maintaining the tunnel, which had become an important water supply for Courtaulds. The mine finally closed in 1987.


Arranged by County and then by Township. Geological Maps have their own section.

The plans described in this volume were collected together in the 1930s, when a working catalogue of them was compiled. They were given a reference consisting of a letter and numbers (eg El/1). The plans have been renumbered in this list, but the old reference is given at the end of each entry. Most plans relate to those parts of central Flintshire and Denbighshire where mineral rights were leased to the company although there are a few for other areas. The arrangement is from the north of the orefield to the south, similar to that in Bernard Smith's work (see Related Material) and (to a certain extent) the old catalogue.

Access Information

No restrictions.


Please order documents using the alternative reference number (where provided).

Other Finding Aids

A hard copy of this catalogue is available at Flintshire Record Office. Catalogue is searchable online at: http://calmview.flintshire.gov.uk/CalmView/

Archivist's Note

Compiled by Steven Davies of Flintshire Record Office. The following sources were used in the compilation of this description: Holywell-Halkyn Mining & Tunnel Company Plans Catalogue; Guide to the Flintshire Record Office (Flintshire County Council, 1974).

Conditions Governing Use

Usual Copyright Restrictions Apply.

Appraisal Information

All records have been retained.

Custodial History

Deposited by the Holywell-Halkyn Mining & Tunnel Company in 1988.


Accruals are not expected.

Related Material

A good starting point when using the plans is the two portfolios of plans and sections, at a 1:2500 scale, compiled by the mine surveyor, J.A. Jones (D/HM/50-1). Flintshire Record Office holds many other records of the Halkyn District Mines Drainage Co, Holywell-Halkyn Mining & Tunnel Co, and Halkyn District United Mines, received from the mine company and from other sources. Other plans of the mines are among the Abandoned Mine Plans, deposited by the Health and Safety Executive (AB), Grosvenor (Halkyn) MSS (D/GR), and J.A. Jones MSS (D/DM/1183). Plans deposited in connection with Acts of Parliament, 1874-1913, are among Quarter Sessions records (QS/DM).

For a history of the mine, see C. Ebbs, The Milwr Tunnel: Bagillt to Loggerheads 1897-1987 (1993), and on the earlier history of the mines and their production, Bernard Smith, Lead and Zinc Ores in the Carboniferous Rocks of North Wales (Geological Survey: Special Reports on the Mineral Resources of Great Britain, XIX, 1921).