Lord Conrad Black, former chairman of the Telegraph Group, which owns 50% of the Docklands print plant, has gained approval to challenge the sale of the group in a Delaware court on the grounds that the sale may require the approval of Hollinger shareholders.

The legal challenge is likely to delay the finalising of the deal with the Barclays, which is currently planned for 31 July.

As soon as a deal is struck, Express Newspapers, which owns the other 50% stake in West Ferry, will have 42 days in which to trigger a change of control clause giving it the right to buy out the Telegraph's share.

A spokesman for Express Newspapers said last week: "We welcome the Barclay brothers with open arms and hope the deal is concluded, and we look forward to meeting them."

Although the date for the change of control is not yet fixed, it looked increasingly likely that Ex-press Newspapers owner Richard Desmond would attempt to buy out the printworks after it emerged that he had registered three possible names for his proposed London evening freesheet.

Express Newspapers has registered the names Londoni, London i and Night Express with the Patent Office.