This is because it is one of the following:

1. It is a photograph created by the United Kingdom Government and taken prior to 1 June 1957; or
2. It was commercially published prior to 1963; or
3. It is an artistic work other than a photograph or engraving (e.g. a painting) which was created by the United Kingdom Government prior to 1963.

HMSO has declared that the expiry of Crown Copyrights applies worldwide (ref: HMSO Email Reply)
More information.

See also Crown copyright artistic works.

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• The Indian Copyright Act applies in India, to works first published in India.
• According to The Indian Copyright Act, 1957 (Chapter V Section 25), Anonymous works, photographs, cinematographic works, sound recordings, government works, and works of corporate authorship or of international organizations enter the public domain 60 years after the date on which they were first published, counted from the beginning of the following calendar year (ie. as of 2013, works published prior to 1 January 1953 are considered public domain). Posthumous works (other than those above) enter the public domain after 60 years from publication date. Any other kind of work enters the public domain 60 years after the author's death. Text of laws, judicial opinions, and other government reports are free from copyright. Photographs created before 1958 are in the public domain 50 years after creation, as per the Copyright Act 1911.

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