In these writ petitions common questions are raised challenging the orders passed by customs authorities on the basis that Tariff Heading 98.01 does not apply to the photographic machinery imported by the petitioners in view of the definition of "industrial plant" in the Project Imports Regulations, 1986 which came into force on April 3, 1986. In three of the writ petitions which were filed in 1986 long before the other petitions were filed, some additional contentions are advanced resting on an interpretation of the said Regulations and the doctrine of promissory estoppel.

2.The three writ petitions filed in 1986, are at the instance of the same person with reference to the same import. The petitioner is a partnership ........ manufacture of colour film, processing and printing and enlargement of the same as a Small Scale Industry. It placed an order for import of two mini colour laboratories from Japan, one for their factory in Madras and the other for their branch in Madurai at a total cost of Rs. 15, 62, 000/- (c.i.f. value) in October 1985. The Letters of Credit were opened on 23-1-1986 and the dates of shipment were 31-3-1986 and 2-4-1986. The goods arrived at Madr