[exim] no queue_run started for several hours

anyone know why this might be?

2011-07-22 07:20:11 Start queue run: pid=32323
2011-07-22 07:25:11 Start queue run: pid=2015
2011-07-22 07:30:11 Start queue run: pid=5038
2011-07-22 07:35:11 Start queue run: pid=8268
2011-07-22 07:40:11 Start queue run: pid=10650
2011-07-22 08:05:11 Start queue run: pid=25082
2011-07-22 08:15:11 Start queue run: pid=31343
2011-07-22 09:20:12 Start queue run: pid=6111
2011-07-22 09:55:11 Start queue run: pid=28711
# date
Fri Jul 22 14:17:58 BST 2011
#
# ps ax | grep 28711
28711 ?        S      0:00 /usr/sbin/exim4 -q
#

does this mean I have a queue running since 09:55 (its now 14:17) and I can
only have one queue running at a time?


thanks,

oliver