[nagrom]

Well, there are very few projects where someone can make a real difference from day 2 or 3. But given that there are numerous permie developers who want either to be a) Product Owners, b) Software Architects or c)professional Youtube viewers, getting a contractor in means you can cut your losses at the end of a 4 week period if you want to and firms do. While it's possible, I've never seen a permie cut during the probation period.

What did you do instead? There is a wave of people looking to get out of contracting in the UK right now exactly because of the messes HMRC keep making.