HR co-ordinate meetings for the new starter with:
HR and training team
IT support
line manager

Manager co-ordinates meetings for the new starter with:
own team
key colleagues

HR contacts with new starter:
first day welcome and overview, tour if office-based
first week check-in and answering queries, making sure set up on self-service HR portal
first month pensions and payroll chat

In the 2nd month we would check in with the line manager to ensure all was going smoothly.