When a business works with a mentor or mentors the key things they need to consider is the way in which their mentor works.  

A mentor is someone who offers their knowledge, wisdom, and advice to someone with less experience.

To me this knowledge, wisdom and advice is all about business experience not personal belief. This personal belief could kill a business idea dead in the water. In this case it nearly did.

In this example the key factor that the mentor should have been looking at was getting research data on the concept. This would have given the business more support for what they wanted to do and i suspect that is why they ended up with an 80 pager after working with Virgin start ups.

If you looking for a business mentor then you may want to consider the following:

What support you need?

What success have they had previously?

Can they help connect you to other sources of support?

Do they fit with you?

Will they drive you forward?