Excel workbook slow to close when other workbooks open

[Andrew.Noble]

Hi

I have a large (>20mb) Excel file (xlsb) that opens and saves reasonably quickly, but takes up to a minute to close (even without saving) if there are other (non-linked) workbooks open at the same time. If no other workbooks are open, it closes almost instantly.

Has anyone ever experienced this and know what the issue may be?

Thanks, Andrew.