Zend certified PHP/Magento developer

How to recover contents of an external hard drive with a corrupted partition table?

I have a WD Elements 5TB USB hard drive that fdisk -l now shows as a single partition of Microsoft basic data:

Device     Start        End    Sectors  Size Type
/dev/sda1   2048 9767473151 9767471104  4.6T Microsoft basic data

The last time I used it it contained 2 partitions in NTFS format as supplied by the manufacturer.

I have no clue as to what corrupted the partition table, but possibly the data is still present on the disk and can be recovered. Can anyone advise me as to procedure to follow, linux tools to do this?