Completely delete pending messages from Skype on Mac OSX

When you send messages on Skype they are only delivered when you are both connected to the Skype network.  If you send a message while either you or your friend is offline you see that it is pending and will be delivered next time you both connect.  

If you send a message and then change your mind you can right click on the message and choose to remove it.  You friend will be sent a notification that you removed a message which is a bit annoying because then they will wonder what you are hiding!

To delete messages permanently and without the notification you need to hack Skype's database which uses Sqlite:

First shut down Skype because it locks the database.

in Terminal

> sqlite3 Library/Application\ Support/Skype/YOUR_USER_NAME/main.db

sqlite> select * from messages

Now find the id of the start of your conversation.  The id is the first column in the results.

sqlite> delete from messages where id > 2904;

This will delete all messages after your conversation.  If you want to be more specific then you may be able to delete individual messages.