OK this is slightly outside the remit of the forum, so I'm just going to give you a personal opinion of what I would do if I were in your position. If you can afford the bankrupty petition fees, then this seems to be the most sensible route. It crystallises the position, and allows you to deal with someone commercial - ie a Trustee in bankruptcy, who will look into your case and investigate the claim. They also have powers to trace and seek out assets, and from the facts you have presented it seems that this is necessary.
Now what I would do if I were to be appointed the Trustee of this case. Firstly, the debtor would have to produce a detailed statement of affairs, and the Trustee will also look into all property transactions which have occured during the last 5 years - or more if there are strong grounds to suspect assets have been moved out of the reach of creditors. A DVLC search can also be carried out with regard to motor vehicle transfers. The Trustee is obliged to follow up all lines of enquiry which may led to assets on behalf of the creditors, and does have very wide powers to bring your former colleage to account for his actions.
As principle creditor, you are allowed to choose an insolvency practitioner of your choice to act as Trustee, and you can then assist the Trustee with his/her enquiries. Make sure that you find someone with experience of carrying out this sort of investigation.
Hope this helps - if you want to ask anything else please post.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk