RE: BMN - The summary8 Mar 2020 15:21
YTSS - the amount that the SP moves following an excess of buys or sells varies wildly from one day to another. Thus there is no guideline as to how much it moves if there is a 30K sell of a 100K buy. It all depends on the situation - that is to say the history of what has happened with each Market Maker before (i.e. their position), the strategy that they may be playing (eg a shorting strategy or selling down a tame seller's block that they may have secured) and their view of the future (both the short-term traders' sentiment and their expectation of news ahead, depending upon how much they may have managed to glean from their buddies the brokers.)
In the case of friday it would appear that the Market Makers were simply taking advantage of the Corona panic to try and target some leveraged holdings sub 19p in order to get shares cheaply that would fulfil their own requirements to close a short, or to stock up ahead of big news coming.