SQL*Loader - Physical record longer than the maximum

Was getting this error in sqlldr:

SQL*Loader-510: Physical record in data file (data.csv) is longer than the maximum(1048576)

Originally I attempted to set the READSIZE option, in the control file:

OPTIONS(READSIZE=10000000000)

However no value was large enough.

Eventually the problem was found to be a corrupted CSV file.