Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How do I find the mappings between sedol and isin codes? 
There is a relatively straightforward transformation explained on the Wikipedia page here and on the links from that page.  Note that this only applies to SEDOLs for instruments listed on the London Stock Exchange (LSE). To convert SEDOL to ISIN you pad leading zeroes onto the SEDOL until you have 9 digits.  Then you add the two letter country code (as defined in ISO 3166-1) to the front.  Then you add a final checksum digit to the end, again as defined in the algorithm on the Wikipedia page. To convert ISIN to SEDOL you do the reverse: remove the final digit, remove the two leading letters, and strip off any leading zeroes. Example: