Based on the provided legal document, here are the key points:

• The petitioner, an ex-serviceman, challenged the cancellation of his D-Form patta dated 29.06.1976, which was ordered by the Joint Collector after a series of confirmations by appellate and revisional authorities. (!)
• The revenue authorities cancelled the patta on the ground that the petitioner never cultivated the land assigned to him, despite the petitioner submitting detailed explanations and documentary evidence to the contrary. (!)
• The cancellation order was initiated at the instance of respondent Nos. 4 and 5 (the petitioner's sons), who claimed they were in possession of the land and sought its assignment to them upon payment of market value. (!)
• The petitioner argued that the cancellation was illegal and arbitrary because it occurred nearly 30 years after the patta was issued, violating the principle that such action must be taken within a reasonable time. (!)
• The petitioner relied on previous judgments (Sekhari Antna Kumari v. Dist. Collector and Madamaneni Chimzaswamy) to support the argument that cancellation after a long lapse without a proper show cause notice is impermissible. (!)
• The revenue authorities failed to consider the petitioner's explanation that, under BSO-15, cultivation could be done by family members, and they did not conduct an enquiry to verify the genuineness of the patta before cancelling it. (!)
• The show cause notice issued to the petitioner did not specify the violations of the D-Form patta conditions, nor did it issue the notice immediately after the expiry of the three-year cultivation period as required. (!)
• The High Court allowed the writ petition, set aside the impugned orders of cancellation, and directed the revenue authorities to issue a proper notice to the petitioner if they intend to verify the genuineness of the patta or check for condition violations. (!)