Thanks for the replies, and sorry for the delay in updating this thread. I have finally had the chance to go through and reboot every ESXi host which has access to that datastore. However, I am still unable to delete the VMDK file. I have renamed the VMDK file and moved it to a different folder, but was still unable to delete it after this. The VMDK is about 1.5TB in size (which is why I am keen to get rid of it). It was only in place temporarily for testing and was never backed up.
