Apologies in advance that I kind of went off on one here

Realistically, grade 1 in a relatively short time frame for an experienced and accomplished musician like Barry wouldn't be that big an issue, especially on a melody line instrument.
Even if one is learning an entirely different instrument, with a new clef, the knowledge, experience and other advantages an advanced musician brings to a new instrument is simply enormous. Sense of pitch, sense of pulse, sense of rhythm, wide knowledge and appreciation of music... seriously, I could go on and on! These are all things that most beginners will take a while to learn and which many advanced musicians will find as natural as breathing.
Some instruments transfer skills better than others, of course, and each person will have instruments they do or don't "click" with, but even so, at G1 level the already acomplished musician has a
wealth of knowledge and experience to help them in preparation and in the exam room that the beginning musician can (usually) barely dream of having.
Passing G1 for a "normal" (for want of a better word) G1 student is one thing, G1 for someone who is highly proficient on one or several other instruments is a different ball game entirely. Learning a new instrument and being a beginner again can be immensely frustrating, and has pitfalls and difficulties all of its own, but those of us who have a good deal of music under our belts so often have an easier ride in so many ways than children and adults who are genuinely starting from nothing. (Those who teach or play full time for a living also have another disadvantage in amongst the advantages of course, in that music practice can end up feeling like an extension of work, not an escape from it!)
I'm very grateful for that and I have to acknowledge, as I have before, that adults especially who are learning entirely from scratch get huge, huge admiration and respect from me for that - I can't imagine what guts and determination it must take when one has no musical background at all and has to start out from the musical equivalent of "A is for apple...". I feel quite awed at the dedication so many adult starters put in.
It's the one thing that sometimes makes me feel a bit of a fraud describing myself as an adult learner. I often try and stretch my musical wings, but the language, aurally and theoretically as well as practically, of music is something that's been part of my life for 24 years. It's an
enormous advantage, and I can't ignore the fact that it makes life appreciably easier for me - it would be disingenuous to downplay it or make out that it was a level playing field.
The only analogy I can think of is when several 4th year students in my year (I was among them), having just returned from a year in Russia, took a class in beginners' Croatian (a related but in many ways quite different language) with a group of 2nd year students (most of whom had had only a year of Russian). There was no getting away from the fact that, although we might all occassionally slip into Russian instead of Croatian, or get muddled between Cyrillic and Roman scripts, or muddle grammar between the two languages, overall we had an enormous advantage; not least that we just weren't phased by speaking and writing in a new language. The class was hugely easier for us in many ways than it was for the 2nd years.
Anyway... straying quite badly off the topic, aren't I? Sorry. Quite honestly, if Barry wanted to take G1 next term, I wouldn't bet against him, and I'd be far more surprised if he didn't pass than if he did - it's just being realistic. Obviously I'm not trying to guilt trip Barry into it (honest!

no seriously, he should only do it if he wanted to) just putting it in perspective