Great Western Coffee Shop

I travelled on the 14:08 Portsmouth to Cardiff service today (but only as far as Temple Meads).  Also travelled on this same service three weeks ago.

On both journeys, I noticed there was a single guard on the service from Portsmouth Harbour.  Ticket checks as usual: after Fareham, Romsey and Salisbury.

But at Westbury, the "voice of the guard" over the PA changed to a bloke.  The original guard was still on the service checking tickets after every stop and doing the doors at Dilton Marsh and Avoncliff.  She was referred to as "the collector" by the male guard.

She also checked railcards quite closely - two people around me had out of date railcards.  One was let off with the railcard confiscated as it was just one day out of date.  The other had to pay an excess.  She was checking dates of birth on child tickets - someone with a DOB in April 1994 tried telling the guard he was only 15.  Her reply was "didn't they teach you maths at school".  Shut him up, especially after parting with ^4.90 for the excess fare :D

Is the presence of a second guard going to be a regular fixture to crack down on fare dodgers on this reasonably busy service?

TM's/Guards/Conductors quite often travel as CS (Customer Service) much like drivers often travel PAO (Passenger As Ordered) where there is a surplus of one or the other at any particular time.  For example, you'll usually find two TM's working the 21:48 Paddington to Worcester from Oxford of an evening because there just happens to be a surplus of 'up' trains in the later evening which are assigned to Worcester depot meaning two of them are booked on the same train home - the last of the day.  They'll usually share the duties with one doing the doors and one checking tickets and assisting.

So, rather than a regular fixture to crack down on fare dodgers, though possible, it's more likely to be a case of staff positioning.

More likely staff positioning or booked assist, although a number of late evening services are double manned to try and combat the rising incidents of anti social behaviour which are a regular feature of some journeys.

Just out of idle curiosity, when there are two guards on a service I assume one is designated as being "in charge" and the other "assisting" to avoid any possible confusion. Is the division of duties something they decide between themselves or is it specified by their diagrams?

It is specified by their diagrams, but in reality they might come to an agreement.  For example if the same two staff are working the same train two days in a row, then they'll share the commission on ticket sales by doing the tickets one night each.  As long as they like each other.