Hindustan Petroleum Corporation (HPCL) and UK-based British Petroleum (BP) Plc signed a letter of intent envisaging a strategic partnership for refining and marketing in India, and joint participation in areas of mutual benefit to both the companies.According to a release issued by HPCL to the BSE today, apart from broad areas to be agreed for strategic partnership, this would also include participation on setting up of the grassroot refinery in Punjab including supply of crude as well as marketing of products.