By Andy Silvester British post for British doors, then, even if it arrives three days late? That certainly seems to be the Square Mile’s assumption, with shares in Royal Mail owner IDS only nibbling up 4 per cent or so yesterday despite news of a bid far north of its existing price. The working theory is that Daniel Kretinsky’s bid won’t get past regulators or government. We aren’t so sure. The investment case at IDS is fairly straightforward. One part of its business, delivering parcels, makes a bucketload of money and is widely understood to be on its way to greater growth. The second part o…