A rule on the London Stock Exchange that allows market-makers to delay reporting any trade more than three times the normal average size for up to ninety minutes. The stated justification is that market-makers need an edge to compensate for their exposure; the practical consequence for VSA is that volume data on any single bar can be corrupted because trades from the previous bar may be reported during the current bar, affecting two consecutive bars. The deeper insight: professionals hide the volume, not the price—because volume gives away their intent.