The bid is being led by Leon Allen, the non-executive chairman of the sausage skin maker Devro, and is backed by Prudential Venture Managers, one of the City's largest venture capital funds.
The deal is thought to be one of the biggest buy-ins in the UK during the 1990s.
Tetley is the leading brand in the UK and is the second most successful tea brand in the world. Lyons, as the company was then called, opened the world's largest tea factory in Greenford, Middlesex, in 1921.
Prudential Venture, an arm of the Prudential Corporation that has £191m invested in a portfolio of 125 companies, only came into the deal as lead backer recently, after the development finance arm of Morgan Grenfell pulled out.
Prudential Venture recently led and negotiated another sell-off from Allied, the £32m buy-out of Lyons Seafoods.
One City analyst said on Friday that an early sale of the beverages business would be viewed very positively in the stock market. Allied's shares rose 1p to 532p on Friday.
In his mid-50s, Mr Allen, a US businessman with a soft spot for Scotland, spent 18 years with Procter & Gamble before eventually moving on to RJR Nabisco in 1982.
He came to the attention of City investors following a £220m management buy-out of Del Monte's juice and tinned fruit business. The company was later sold to Royal Foods of South Africa for £360m.
As a non-executive chairman of Scottish-based Devro, Mr Allen received a £200,000 bonus for presiding over the company's flotation on the London stock exchange at the end of June 1993. The shares were issued at 170p and immediately jumped by 18 per cent. They are now trading at 242p.
Allied, the first maker of the circular tea bag, was rumoured to have been offered £400m for its Tetley tea business last autumn by Nestl, the Swiss-based consumer group.
Neither Mr Allen nor Prudential Ventures were available for comment. A spokesman for Allied merely said that any sale would be in accordance with the company's stated policy.
Allied Domecq announced its plan to withdraw from its food businesses a year ago after Allied Lyons, as the company was known then, bought Domecq, the Spanish spirits company for £739m. That deal took Allied to second place in the world league of spirits companies (behind Grand Metropolitan) and catapulted the company into Latin America, giving it 40 per cent of the Mexican spirits market: £143m of the proceeds was divided among the 500 or so members of the Domecq family who accepted the purchase.
In July, Michael Jackaman, Allied's chairman told shareholders: "We have said we plan more disposals, to add to the £400m plus already achieved in the last two years."
Tetley is involved in a $10m (£6.2m) court battle against Thomas J Lipton in the US over claims that Lipton had hijacked the round tea bag.
Tetley's lawsuit claimed that the round shape was not functional but was an " arbitrary and unconventional means of identifying" the company's goods.Reuse content