The former owner of Britain's remaining coal mines said its property arm was making good progress and was well-placed to cash in on strong market demand.Coalfield Resources, whose only significant investment is a 24.9% shareholding in Harworth Estates, said Harworth continued to make progress across its range of sites in generating income, increasing valuations and disposals.Coalfield, which used to own the UK's biggest coal miner UK Coal until December 2012, said the property market in the regions in which Harworth operates continued to show signs of improvement and was giving it a foundation for growth.Harworth, which owns a range of former mining sites and related property, has sold assets this year including land at Cannock, Staffordshire, and two further commercial plots at its advanced manufacturing park in South Yorkshire, all at above book value. Coalfield split its operating business into two separate units - property and mining - and gifted 75% of the property business to the trustees of the mining business pension fund.It also gave up control of the coal mining operations to an employee benefit trust, retaining only a minority equity stake which ranked behind the debt owed to the pension funds. Following a fire at one of the mines last year which caused a failure and restructuring of the mining business, Coalfield no longer has any equity interest in the mining business.Shares were flat at 6.12p at 09:31 in London. PW