Question on rolling forward AIs

So I'm trying to roll my archived AI files forward onto a database that was restored from last night's backup. We are using the AI Archiver. I've found the archived AI file that is the correct one to be applied next (based on the timings of things). I've tried to apply it using roll forward, but I get the following in the logs:

[2015/05/19@13:10:10.102+0100] P-3784       T-1904  I RFUTIL   : (451)   Roll forward session begin for inencoadmin on CON:. 
[2015/05/19@13:10:10.104+0100] P-3784       T-1904  I RFUTIL   : (7129)  Usr 0 set name to NETWORKS\inencoadmin. 
[2015/05/19@13:10:10.105+0100] P-3784       T-1904  I RFUTIL   : (15321) Before Image Log Initialisation at block 0  offset 555. 
[2015/05/19@13:10:10.118+0100] P-3784       T-1904  I RFUTIL   : (660)   Beginning roll forward of after-image file \\tera\E\Progress\Servers\Hob\E_AIARCHIVE\SECURE\j!~database~secure~secure.20150415.001039.00000716.secure.a68. 
[2015/05/19@13:10:10.132+0100] P-3784       T-1904  I RFUTIL   : (8019)  Expected ai file number 1 but file specified is 716 in sequence. 
[2015/05/19@13:10:10.133+0100] P-3784       T-1904  I RFUTIL   : (11014) roll forward open \\tera\E\Progress\Servers\Hob\E_AIARCHIVE\SECURE\j!~database~secure~secure.20150415.001039.00000716.secure.a68 error: -1. 
[2015/05/19@13:10:10.137+0100] P-3784       T-1904  I RFUTIL   : (15109) At Database close the number of live transactions is 0. 
[2015/05/19@13:10:10.138+0100] P-3784       T-1904  I RFUTIL   : (15743) Before Image Log Completion at Block 0 Offset 555. 
[2015/05/19@13:10:10.182+0100] P-3784       T-1904  I RFUTIL   : (334)   rfutil -C roll forward session end. 

The thing is, we no longer have file 1, or 2, or anything up to about 650. We've deleted them as we've taken backups. We are of the impression we don't need these files any more. 

(Before anyone says, yes we should have tested this ages ago!) 

Progress 11.5.