According to a London Stock Exchange announcement, in a transaction reported on 14 June Liontrust increased its position from 2.26 million to 5.21 million shares.
Based on Charles Stanley's closing price of 360p on that day, the additional investment was worth around £10 million, with Liontrust's overall stake valued at a little under £19 million.
'When reviewing investments we look for distinctive characteristics in a company which we believe give it an economic advantage; intellectual property, strong distribution channels, and significant recurring business,' Tong told Citywire.
The transaction came on the same day Charles Stanley unveiled its full-year numbers, which showed the firm back in the black after a restructuring under chief executive Paul Abberley (pictured).
The results revealed a pre-tax profit of £8.8 million in the 12 months to the end of March versus a loss of £0.3 million in the previous year. Core business revenue rose to £138.6 million from £133.5 million in the previous year.
'The strategy determined in early 2015 required considerable preparatory work but I am pleased to be able to report that this is now largely in place and the benefits to both clients and shareholders are materialising,' Abberley told the market.
If Abberley continues to deliver, Tonge sees potential for further gains.
'We believe that management at Charles Stanley are successfully improving the business through a mixture of reorganisation, cost control and a greater focus on recurring income
'The longer-term goal is to achieve higher margins that are more comparable with competitors. If this can be achieved the shares will deliver further gains.'
In the 12 months to the end of May the Liontrust UK Microcap fund - which is managed by Julian Fosh, Anthony Cross and Victoria Stevens alongside Tong - has returned 29.7% versus a sector average of 27.2%.