API said talks after a "preliminary approach" made a month ago had ended and "as a result it is no longer in an offer period".

The mystery bidder was revealed as Illinois Tool Works.

Chairman David Hudd said: "We are pleased this period of uncertainty is now over. The directors are confident of the firm's ability to deliver an appropriate return to shareholders as an independent entity."

Reports suggested the offer was between 200p and 215p per share and it is believed shareholders, the largest being USA's Steel Partners, wanted more.

The announcement follows a flurry of selling activity at API. Five months ago it sold its loss-making metallised paper business in Caerphilly to a management buy-in team.

A month later it sold the converted paper division for 12.2m to its two directors. And in February it broke news of the preliminary approach by an unnamed company. Last month the firm's share price hit a 52-week high of 189.4p.

Story by Jez Abbott