I was thinking about what would prompt the sudden boost in...

I was thinking about what would prompt the sudden boost in trading to 51m shares in a stock that is normally so illiquid.

I've figured it out: whoever has entered into the contract to buy Bentley's shares is snapping up as many shares as possible before settlement of the transaction with Bentley.

The reason is that they want the block trade with Bentley to be the transaction that pushes them over the 20% threshold that triggers a requirement to launch a takeover bid. In other words they're snapping up stock on the cheap before they launch their takeover bid at the same price that they paid Bentley (i.e., 26.5cps).

Look at the market depth. There are very few buyers queued up, which means that whoever is buying isn't your average retail punter with his small 'at limit' orders.