The file is a report written in OpenOffice. Not my file so I don't know what happened to it. I have been asked if I can help sort it out.
file command outputs 'OpenDocument text'
File is confidential so can't post up.
Since last post I have managed to extract the text content by a roundabout route - select all content, copy and paste into Quanta, select view which displays the text, copy the text and paste into a new doc in LibreOffice, save as .doc file. The text is completely unformatted so will need paragraphs, line breaks, etc added but at least the text is not lost and won't need to be retyped (report is 16 pages long).
So, have solved the problem for now but I still would be interested to know why it can't be opened properly in OpenOffice.
Thanks for all help.