Utilico Investments, a UK investor managed by Infratil director Duncan Saville, reaped $30.7 million selling down its stake in Infratil with the shares trading near a seven-year high.

The investment firm, which once counted Infratil as its biggest holding, yesterday sold 10.4 million shares on market at $2.95 apiece, according to documents lodged with the stock exchange. That lowered the investor's stake in Infratil to 6.9 percent from a previously disclosed 8.8 percent level. The shares rose 0.7 percent to $2.99 today, and this week were near their highest level since October 2007.

The UK investor used to be known as Infratil International, whose directors included Saville, one of the original directors and a founder of Infratil, and had already reduced its stake in December 2013 from 13.3 percent.

Infratil counted 15,592 investors on its share register as at May 19, the biggest being the Accident Compensation Corp's investment unit with 8.9 percent. The 90-day average trading volume in Infratil shares is about 770,000.

In October, JML Capital, an entity related to HRL Morrison - Co chief investment officer Lib Petagna, sold 3 million shares on market, reaping $8.43 million, according to a notice to the stock exchange at the time. JML held 11.42 million shares as at May 19, or 1.95 percent of the company, according to Infratil's annual report.

Infratil shares got a boost when last September's general election returned the incumbent National-led government, removing the threat of electricity regulation that would have reduced the value of some of the company's investments.