It was so big that clearing it was a 6 week activity. Since the first trial system copy was done 2 weeks into the project, the table was still huge :-)
Second trial run starts next week, the table has been cleared down.
Unfortunately there is no hack to truncating the table as far as I can see - it is linked into other tables so you have to use the delete program.
By the way the delete program then completed in 4h on HANA instead of 6 weeks on a regular DB.