The fund reaching its limit coincides with its official third anniversary, although it was launched in August 2007 with seed capital.
Existing investors will be able to add to their mandates on request and any outflows will be recycled to new investors as appropriate.
Majedie said it has consistently maintained its commitment to closing its funds to new investors once capacity limits are achieved, in order to protect client performance.
Since inception (31 August 2007) the fund has returned 88.1%, compared to 2.3% from the FTSE All-Share Index, and 2.6% from the Dow Jones CS Long/Short Equity (GBP) Index.
Its annualised return over the same period is 15.7%, compared to 0.5% from the FTSE All-Share and 0.6% from the Dow Jones CS Long/Short.
Last year the fund returned 10.8%, while the first benchmark lost 3.5% and the second 7.8%.
Robin Harris, managing director of Majedie, said: "Since launch Matthew and Chris have performed well in difficult markets, generating a record that has been rewarded with consistent inflows into the fund.
"We have always maintained that the Tortoise Fund capacity is both precious and finite and have stuck firmly to our original capacity limit. Size is the unspoken, structural impediment to making money."
Portfolio managers Matthew Smith and Chris Reid joined Majedie in 2006 and 2008 respectively. Both previously worked as Pan-European analysts at Deutsche Bank and Credit Suisse.
