LONDON, JAN. 20 -- A letter was submitted to the British High Court this week to try to show that there was a direct involvement of Washington lawyer Thomas J. Ward in the Guinness PLC case, Britain's long-running financial scandal.

The Guinness case involves several hundred million dollars in allegedly illegal stock purchases by the British beverage company's senior management and allies aimed at helping Guinness acquire the Scottish liquor company Distillers Co. Ltd.

On Monday, counsel for Britain's takeover panel, the official body that polices merger and acquisition activity, submitted as evidence in a High Court hearing a letter in which Ward, then on the Guinness board, was said to have promised to fully reimburse a Swiss company, Pipetec AG, for its purchase of $112 million worth of Distillers stock. Such a confidential agreement could be a violation of the panel's rules against "undisclosed concert party" arrangements.

{David Aufhauser of Williams & Connolly, Ward's Washington lawyer, said Ward denies violations of takeover panel rules. "There was no breaking of any takeover regulation or code," Aufhauser said. "If there was one, there was certainly no knowing break."

{Aufhauser also said there was no allegation of violation of law, only the takeover panel rules, which he likened to New York Stock Exchange regulations. The question before the court, he said, is whether Guinness can be penalized civilly for violations of the takeover panel rules.}

The letter, signed by a Pipetec official and countersigned by Ward, was dated April 18, 1986. In another letter dated April 17, also introduced as evidence, Guinness' finance director wrote to the director general of the takeover panel to confirm that "no financial arrangements" had been made with Pipetec.

Pipetec was a subsidiary of Swiss-based Bank Leu. Bank Leu's chairman, Arthur Furer, was on the board of Guinness until he was forced to resign in the aftermath of the scandal.

Pipetec bought its block of Distillers shares, 3 percent of Distillers' equity, one day before Guinness won control of the company, said Neil Fagan, a lawyer acting for the takeover panel.

"There is no doubt," he said, "that this block of shares was a key factor in the takeover. From my point of view, Mr. Ward played a very significant role in the takeover."

The High Court hearing, expected to run into next week, arose when Guinness challenged a September 1987 panel ruling that Guinness had used undisclosed concert party arrangements in its Distillers' takeover. If Guinness loses the hearing, the company may be obliged to pay out hundreds of millions of dollars in compensation to stockholders in Distillers at the time of the takeover.

Ward, 47, a senior partner at the Washington law firm Ward, Lazarus, Grow and Cihlar, is appealing a July 1987 ruling by the British High Court that a payment of $8 million for his advisory services to Guinness during the Distillers bid was "unlawful." In January 1987, the board of Guinness fired Guinness chairman Ernest Saunders and demanded the resignations of Ward and Furer.

Under Britain's decentralized system of financial regulation, action in the Guinness case is proceeding on three official fronts, as well as private lawsuits like the Guinness effort to get back the $8 million it paid Ward. Britain's Department of Trade and Industry is in the midst of a secret year-old investigation, and last October the fraud squad division of the London police arrested four alleged participants, including former Guinness chairman Saunders, on criminal charges including theft, falsifying invoices, and "conspiracy to create a false market" in Guinness shares.

A fifth alleged participant, London stockbroker Tony Parnes, was arrested in Los Angeles, and the British police are seeking his extradition.

The third front is the takeover panel's investigation. In this week's hearing Guinness is arguing that the panel should await the Department of Trade and Industry's findings before making any rulings. But the panel wants to move as quickly as possible, according to a spokesman, Peter Fraser.

"If we're right," Fraser said, "a lot of people could be owed a lot of money. We don't think it's right to wait two or three more years before they get it."

In the Pipetec letter, Ward was said to have agreed not only to buy back the 10 million Distillers shares at the purchase price, but also to pay all of Pipetec's commissions, fees, and taxes in the stock purchase, a margin of one eighth of one percent over Pipetec's funding costs, a commission of 0.1 percent to Pipetec, and an arrangement fee of $70,000.

The British government got its initial tip-off to the Guinness affair from information given to U.S. authorities by convicted insider trader Ivan F. Boesky.