No locked off youth gearing restriction for road racing British National Series/Championships Can anyone correctly confirm (by providing a link to the exact rule in British Cycling rulebook), if the use of locked off gears is permitted in Youth (A, B and Junior) National level series or championship road races? We have had experience of different rulings this year, 2017. 

I cannot find any reference to this rule on the British Cycling website, but have found reference to it on a forum that didn't specify any country, and also a page on US Youth Cycling.

UPDATE: Further advice/comment we have received is that there is a International/UCI (race) ruling stating that youth (A, B, Junior) level are not permitted to use locked off gears, and that the full range of cassette/rings must be within the limitations of that category. Whether British National Series events are included within this appears to be on a race by race basis - and the best advice I can give anyone reading this post is to (a) check well in advance of any race what the ruling is to be applied on the day and (b) you may as well go out and buy from the start the correct limited gears.
A year and a bit on, I'd like to answer my own question. In the UK, I've not seen anyone turned away from National Championship races for having locked off gears, and the ruling that was sent to us, wasn't necessarily implemented at the event we attended. 

However, if you are going to race in continental Europe (such as Assen Youth Tour, or any other race for that matter), then you have to ride on a specific chainring and 10 or 11 speed cassette for your category with full range, and this therefore, is not locked off. We therefore had to switch to this format for all our bikes (spare wheels as well, of course), and thus you negate the whole need to lock gears off. As I stated in my original question, the best advice is to fit the bike from the start with the appropriate cassette (you'll have to dig around to source them).