If Stuart Chambers, the glass maker's chief executive, were to leave the merged group, he also could net a substantial sum - close to £3.7m, including shares worth £1.7m, options of £920,000 and a £1m contractual payoff.
Sir Nigel, 58, like his four fellow non-executive directors, is paid in shares. He has been with the company since 1994 and its chairman since 1995. He is also chairman of Boots, where he is negotiating a £7.5bn merger with European pharmacy firm Alliance Unichem.
Already Nippon holds 20 per cent of Pilkington, which is twice its size, and has an agreement with the UK company to supply glass to the Japanese car industry. They jointly own a US manufacturing plant.
Nippon first approached Pilkington in October, with an offer of 150p a share, but was rebuffed. It tried again at 158p a month later, valuing the company at £2bn, with the same result. Despite talks reportedly going cold in early January conversations between Pilkington and its advisers, Lazards, and UBS and its client Nippon, continued.
Sources close to the deal now say that the discussions are detailed and coming to a conclusion and that a renewed and agreed offer of 165p a share is expected by the end of the month.
There had been concerns about Nippon's ability to finance the deal as it would involve raising £570m of debt to finance the £1.7bn purchase of the shares it does not own. Last month it also issued a profits warning. When Nippon approached Pilkington in the autumn it was amid a frenzy of merger and acquisition activity. The Spanish telecoms operator Telefonica bid for O2, and Dubai-based DP World began its offer for P&O: both those bids were successful while Nippon's stalled.
Pilkington is one of the world's largest glass manufacturers, with operations in 24 countries around the world and it has some 23,800 employees. Based in St Helens, Merseyside, it was founded in 1826, and was first listed as a public company in London in 1970.
In 2005 Pilkington had a turnover of £2.75bn, two-thirds of which came from European sales, with another quarter in the US, with pre-tax profits of £136m, supplying automotive, building and other industries.
Sir Nigel made his name at Williams Holdings, one of the industrial conglomerates, like Hanson, that grew through aggressive acquisitions during the 1980s. Along with his chairmanship of Boots, he is also chairman of Pendragon Group and deputy chairman of Barclays.