The following concerns might lead you to requesting a restriction to the access of your thesis:
Under UK and most international copyright laws, any significant work automatically attracts copyright protection. This is designed to protect the rights of authors. Authors (or their publishers) can take legal action against those who infringe their copyright.
Your thesis may contain material that you don't hold the copyright for, for example, quotations lengthier than permitted for educational use, images, photographs, graphs, tables, maps, etc. If you have included such material from either a published or unpublished work you will need to have obtained the rights holders’ permission to include their content in the online version of your thesis.
Third-party copyright material can be included for examination purposes (for which the audience is limited to your supervisors, markers and external examiners), but not for open access without permission from the rights holders.
Sensitive information other than personal data
Your thesis may contain content-sensitive information that could mean open access to the full text of your thesis is not feasible. For example, if your thesis includes any potentially sensitive commercial information, any information provided in confidence or information relating to security matters, access to the full text of your thesis should be permanently restricted in the research repository.
The requirements of any funding you have received
If your degree was funded by a Research Council you should check if your funder requires a particular deposit option, as some research councils require an open access deposit. If you have been funded by a commercial or other private funder you should make sure that you comply with their requirements regarding access to the completed thesis
Possible future publication of your research
Access to the full text of a thesis in the research repository can be restricted if you are concerned that including the text may prevent you from finding a publisher for your thesis. You should discuss these concerns with your supervisor before concluding that restricted access is necessary.
If your thesis contains personal data relating to individuals who haven’t given consent for their data to be made available online, access to the full text of your thesis should be permanently restricted in the research repository.