Please answer a question about the following article about Imperial College London:

The College's endowment is sub-divided into three distinct portfolios: (i) Unitised Scheme a unit trust vehicle for College, Faculties and Departments to invest endowments and unfettered income to produce returns for the long term; (ii) Non-Core Property a portfolio containing around 120 operational and developmental properties which College has determined are not core to the academic mission; and (iii) Strategic Asset Investments containing College's shareholding in Imperial Innovations and other restricted equity holdings. During the year 2014/15, the market value of the endowment increased by 78 million (18%) to 512.4 million on 31 July 2015.

What is the term that represents a unit trust vehicle that allows endowments to be invested to produce returns for the lon term?
Unitised Scheme