20 minute interval session on the treadmill at school, waiting for sets of parents to arrive to hear about their offspring - reminds me how dull and noisy treadmills are!
Tried 5 minute mile pace for 1 minute at a time, with a minute of 8 minute mile pace recovery, and that was OK so thought I'd see what 4 minute mile pace felt like.... could barely manage 25 seconds. How do the elite manage it???