The first X8 attempt was the 355
The first X9 attempt i assume was in part the 44
It was the X8/X9 loop,they interworked at Whitley Bay
They then (in part) merged the 56 and X8 which became the X6 but the other parts were the 53A with the 53 going to Whitley Bay (old 343)
Then it became its current format