How does one obtain Letters of Administration from Courts in India regarding estate of Deceased?

We are From England. My parents have been deceased since mid 1970s. They had certain investments in Indian companies and bank accounts in India. I wish to know what is the procedure for obtaining letters of administration to their respective estates? Who can be appointed the adminstrator? Would it be myself as the heir? or does the court have descretion in this respect? Since I am not based in India, Can I give power of attornery to a lawyer or other person to pursue the matter on my behalf. Do I need to have the deatils of the estate? Or is it the function of the administrator to research and obatin the details of the estate?