Hanson, the British building materials company, was bracing itself for a £7 billion-plus bid approach last night after HeidelbergCement, Germany’s largest cement maker, said that it was considering a bid.

Hanson’s shares, which had risen during the day on talk of a possible approach, soared more than 20 per cent after the German group said that it was exploring “the possibility of seeking to acquire the company”.

Hanson’s shares closed yesterday at £10.25, valuing the world’s biggest supplier of sand and gravel for buildings at £7.3 billion. Hanson declined to comment last night but a source close to the company said: “We believe it is friendly; it just depends on the terms.”

It is understood that the German company could approach Hanson with an offer as soon as next week, in an attempt to gain access to its books.

Hanson is what’s left of one of Britain’s great conglomerates of the Thatcher era. At its zenith, it was an empire worth more than £14 billion and was more profitable than BP.

But it gradually broke up, demerging divisions such as Imperial Tobacco. Today what is left is one of the world’s biggest producers of aggregates, such as sand and crushed rock, which are used in the construction industry. The company derives more than half its revenue from the US.

HeidelbergCement’s move comes amid global consolidation in building materials. Hanson has long been the subject of bid speculation, with the French cement giant Lafarge and the Mexican group Cemex both seen as likely bidders.

HeidelbergCement, which is controlled by the German billionaire Adolf Merckle, said this year that it was targeting strategic acquisitions.

Times Recommends

• Minister in talks with Saudis to protect creditors
• Premier Inn hits back in £29-a-room row
• Bankers hit back at 'populist' bonus supertax