HMRC (HM Customs & Excise as it was before the merger with the Inland Revenue in 2005) has a long history, most of which has concerned stopping smuggling and regulating activities such as brewing. This has implications for the character of this part of HMRC.
In the early days of VAT, many officers came from preventive activities at seaports and airports. Some tended to have a confrontational attitude when dealing with their ‘customers’. Thankfully, this attitude is no longer so prevalent as more officers only have experience of VAT.
This background explains why HMRC took so long to come to terms with the concept of professional representation of taxpayers.