He <b>had driven</b> to St. Marie's Hospital as soon as <b>he'd</b> understood what <b>had happened</b>, not waiting to be called, just knowing he would be needed.<br/><br/>Please tell me the sequence of these actions. What happened first? Driving to the hospital or understanding what happened?<br/><br/>Why can't I use 'He <b>drove</b> to St. Marie's Hospital?'<br/><br/>thanks!