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London-based contractor John O’Neill and Partners has fallen into administration.

The £15m-turnover firm, known commonly as Jonap, has carried out a number of high-profile contracts, including a fit-out of Conservative HQ in Millbank Tower.

Two winding-up petitions were launched against the company in recent weeks, the most recent of which was heard last Thursday. Administrator Leonard Curtis was appointed to the firm on the same day.

The firm, founded by Willmott Dixon veteran John O’Neill in 2002, is understood to have been pushed under following disputes over payment on the now complete £100m luxury Corinthia Hotel refurbishment next to Trafalgar Square, on which Jonap was a fit-out subcontractor.

Despite its relatively small turnover, the company had gained a big name in the capital’s high-end residential fit-out and construction market. As well as the Corinthia job, which was for hotel operator CHI Hotels and Resorts, Jonap was also engaged in the £26m construction of the Charles de Gaulle Lycée Francais French language school in Kentish Town, when it fell into administration.

Sources close to that scheme said the main build had been completed and discussions were ongoing with subcontractors in order to complete the fit-out in time for its planned opening in September.

Administrator Leonard Curtis confirmed its appointment but has not yet made any comment as to the impact of the administration on employees and customers of Jonap.

According to its latest accounts Jonap, which is based in Teddington, Middlesex, made a profit of £194,000 in the year ending 31 March 2010, down from £405,000 the previous year.