BRITAIN'S offer of GBP100 million (HK$1.23 billion) in soft loans was the sweetener which helped to secure the package of measures on Hong Kong. But the deal, for the purchase of equipment or services from British companies, is not the biggest in recent years. The first two were issued in 1986 and 1988 for a total of GBP300 million. The second of those was delayed following the Tiananmen Square massacre. All were agreed between Britain's Department of Trade and Industry, China's Ministry of Foreign Trade and Economic Co-operation and the Organisation for Economic Co-operation and Development. A third soft loan of GBP55 million was made last September, for the development of Nanjing airport by Siemens-Plessey.