Having read with some interest the piece by Fred Crouch, ONE ROD V TWO, in Barbel Fisher No5. Surely this option is up to the individual? If one is happy with one or two rods, so what? A lot of factors need to be considered, size of river, nature of swim, and I suppose more importantly, Why?
In Freds article he states that he has "never been a big fish man", and if he fishes two baits it will be using one rod, reeling in and recasting etc. If one is content catching numbers then one rod fished over the baited area will be adequate. However, being a specimen hunter, I often do not find this approach to suffice and find two rods, one being used as a decoy, is much more favourable. Let me explain how I have arrived at this conclusion.
Having spent hundreds of hours up trees etc, watching feeding barbel, there are a few common factors which, scream, at me that to target the bigger fish, the use of two rods (one decoy) is far superior. I have found on heavily fished waters the biggest fish are usually always well back from the smaller feeding fish of the shoal, often refusing to leave the sanctuary of their holding area altogether. They will seldom come up to where the main shoal have their heads down. If they do it is only to pick up a couple of grains of hemp before returning. I have also seen on many occasions that if there is a piece of meat on the hemp, the big fish will not come anywhere near it, they will remain downstream.
If however, one reels in the meat, the big fish will again periodically visit the hemp (I am using an 8-10 ft tail to keep the line flat on the bottom). I have also cast in with no bait on the hook and the fish still visit the hemp, so it is not the line or weight that is spooking them, it is 100percent the hookbait! I have found on unpressured waters the big, dominant, fish will always be the first to investigate a piece of meat or any other food, it would appear they have first refusal. In this circumstance I would favour one rod over two. Unfortunately one cannot frequent these
I do not put any freebies in, as this will:
A.   Destroy the natural pecking order that barbel have, creating a free for all. That will end up with the smallest of the shoal seize my bait, being the lucky chap that I am.
B.  Get the nuisance chub confident
C.  The freebies will be given the all clear after thorough investigation, whacking it with their tails etc, until all that is left is the very suspect hookbait. After some time A or B then happens!
The best WAY I have found to avoid this frequent scenario is to:
First place a nice piece of meat on the business rod downstream near the holding area and tight to the bank. Backwind and walk upstream to the feeding area, or just downstream, place the rod in two rests and attach a critically balanced bobbing. 
Bait up the feeding area with hemp, or whatever particles, and fish normally over it with the second rod.
So long as I am sure in my mind that the hookbait on the first rod is ok, there it will remain until a take.
I will usually get this in motion during what I know to be a moon, dead spell, the main reason for this is that the big fish are usually the first out to investigate. The bait on the first rod will usually have a swarm of minnows, at it. This sometimes results in the barbel swimming up to see what they are up to, or to eat them, when they scatter it leaves the hookbait looking like, food and not bait, often resulting in a quick take.
I am also writing about very educated big fish, not a shoal in a feeding frenzy, or fish that are hardly fished for. Also note that in the majority of swims I am drawing fish from a, holding, area to a feeding area.
I now fish this decoy method nearly always, whether fishing for visible fish, or fish that are not visible in the murky depths of the, Sabrina, as I believe the fish are behaving in exactly the same way. My catches bear this out. Nearly always catching my biggest fish on the downstream rod. I cannot stress enough that if I were to only fish the one rod, the fish are as spooked by it as if it were over the hemp. Resulting in either A and B, above!
There have been odd occasions when arriving at a swim, fish are already there naturally grubbing about, see picture.  I would then favour one rod over two, not wanting to possibly spook them by introducing hemp/particles. I will lower, a single hookbait in, into what I consider a prime spot, these fish do not like being cast at! 
I recall one such day last season, I watched the fish, shown in the picture above, for over two hours before deciding where to place the hookbait. The place decided on in this case was tight to the bank in slack water and on fine gravel that was well sunlit, and would remain so for several hours.  This was about 20yds upstream of the shoal.  Over the next three hours the biggest fish visited it four times. On the fourth a screaming take developed, resulting in a Lugg best of 10.10, which was only 1oz under the official Lugg record.
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THIS GROUP OF 17 BARBEL ARE IN THE LUGG THERE ARE 3 DOUBLES IN THE SCHOOL THEY ARE IN 9FT OF WATER ON A BRIGHT SUNNY DAY. WHAT IS WORTH NOTING IS THAT THE CONCENTRATION OF BIGGER FEEDING FISH, ARE IN THE BRIGHTEST PLACE AND ARE GRUBBING ABOUT ON THE FINEST GRAVEL.  CONTRARY TO WHAT WE ARE LED TO BELIEVE THESE FISH WILL RARELY PICK ANYTHING UP FROM THE SHADED AREAS, THESE FISH ARE CUTE! I TOOK THE BIGGEST LATER THAT SAME DAY AT 10LB 10OZ IT WAS 1OZ UNDER THE CURRENT LUGG RECORD.
 
ONE ROD OR TWO?
 
ONE-ROD-OR-TWO