Dangerous number. Missed the call and they left a voicemail in a robot voice which said: 'Officer of HMRC. If in case you do not press 1 and your call is not connected to us immediately then a warrant will be issued under your name and you will be arrested shortly.' On another site it confirmed that this number is used for scamming people out of money using the HMRC scam. So definitely not a neutral number- ignore their calls and block it.