However I feel obliged to point out that Dando-Collins should be approached with no little caution.
Whilst his writing style is certainly at the ‘exciting’ end of the spectrum the work as a whole is poorly footnoted and prone to portraying conjecture and speculation as absolute historical fact.
For example Dando-Collins would have the reader believe in the Spanish antecedents of Legio X. However the exact details of when and where this legion was raised cannot be stated with any certainty. It is more accurate to simply say that Legio X was established in 59 or earlier.
....he (i.e. Caesar) was appointed governor of both Cisalpine and Transalpine Gaul for five years, with the command of four legions.
App BC ii. 13
Thus it was that the multitude granted him the government of Illyricum and of Cisalpine Gaul with three legions for five years, while the senate entrusted him in addition with Transalpine Gaul and another legion.
Dio xxxviii. 8.5
See also BG i.7 and i.10
There were 15 legions in service in 59 BCE (See Table XIV P A Brunt Italian Manpower). The sources do not break down the deployment of these legions by individual number. However it is generally reckoned that Caesar inherited the VII, VIII, IX and X; described as ‘four veteran legions’ during the battle at Bibracte (BG i.24)
According to Brunt the VII, VIII and IX most probably served under Q. Metellus Celer during the Bellum Catilinae i.e.
Quintus Metellus Celer, however, was stationed in Picenum with three legions
Sall. Cat. 57.2
These are clearly the three veteran legions Caesar found in Cisalpina in 58
Brunt: Italian Manpower
Brunt goes on to argue the X was most probably stationed in the Transalpina in 59
The sources indicate the antecedents of the Transalpina legion date back to 64 when the propraetor L. Murena held a levy in Umbria on the way to his province.
But still Lucius Murena's conduct in his province procured him the affection of many influential men, and a great accession of reputation. On his road he held a levy of troops in Umbria.
Cic. Mur. 42
According to Brunt this legion will have subsequently served under C. Pomptinus praetor of 63, who crushed the Allobrogic revolt in 62-61
Praetor Gaius Pomptinus subdued the rebellious Allobrogians near Solo.
Liv. Per. 102a
The potentially spurious Spanish origins ascribed to the X by Dando-Collins rest on Plutarch:
At any rate, as soon as he reached Spain he set himself to work, and in a few days raised ten cohorts in addition to the twenty which were there before. Then he led his army against the Callaici and Lusitani, overpowered them, and marched on as far as the outer sea, subduing their tribes which before were not obedient to Rome
Plut. Caes 12.1
However it is unlikely the ten cohorts mentioned here comprised the X. It is more probable these cohorts were raised from locally settled Romans and natives in order to form an irregular legio vernacula. This force was then deployed to supplement the regular garrison of Ulterior in its campaign against the Callaici and Lusitani.
Of course one might make a case using Plutarch to posit the X began its life as a legio vernacula, before being esablished on a more 'regular' footing, as subsequently occurred with Legio V. Unfortunately though Dando-Collins fails to explore the alternative, possibly more plausible evidence posted above, in an effort arrive at a more balanced conclusion.