A £4bn recommended offer for British aerospace and defence company Cobham from US private equity group Advent faces scrutiny over national security concerns - and the prospect of a rival gatecrashing the deal with the top shareholder appealing for competing offers.

The board of the FTSE 250 firm is advising investors to back the unsolicited 165p-a-share cash offer, which is at a 34.4pc premium to Wednesday's close.

Shares soared 35pc to 166p on news of the approach from Advent, which manages funds worth $35bn.

Management claims investors were likely to support the bid were dealt an immediate blow by Cobham's biggest shareholder.

However, Silchester International, which has a 12pc stake, said it should “seek others who might offer better value to stakeholders of Cobham” and that the price was not “compelling”.

The investor added: "Cobham's balance sheet has been restored by the public shareholders... management has undertaken a broad-ranging improvement of the business, the fruits of which should flow through in the next few years."

Silchester added that Cobham's "extensive US operations have a strategic value to a buyer with significant North American interests, the current weakness of sterling provides an excellent opportunity."