River Gipping
During 1791, when the Trustees were negotiating with John Rennie, they had asked him to assess an extension of the navigation from Stowmarket to the River Lark at Bury St Edmunds, but this was not pursued. With the navigation thriving, there were two proposals for canals from Ipswich to Eye, Suffolk in 1819. A meeting was held in January at Eye, which was chaired by Charles Cornwallis, 2nd Marquess Cornwallis. It considered two reports, one proposed by the civil engineer William Cubitt, which involved a tunnel through the hills at Mendlesham, with the estimated cost exceeding £100,000, and another, for a canal over the hills, costing £80,000. Both were thought to be too expensive to implement, but a third proposal emerged, for an extension from the River Gipping at Needham Market, which would follow the valley of a tributary through Creeting St Mary to Earl Stonham, where a basin would be built beside the turnpike road (now the A140 road). This would enable waggons to make a round trip from Eye in a single day, rather than the two days that a trip to Ipswich took. The scheme was estimated to cost £12,000, and shares in it were offered at the meeting. Although many were taken up, the scheme did not advance any further.
River Gipping
When the Eastern Union Railway announced plans for an extension from Ipswich to Stowmarket in 1844, the Trustees negotiated with the company to lease their canal. They hoped that this would be of benefit to the shareholders, and that it would help the railway by removing one source of opposition to their plans. They submitted a firm proposal for the lease on 8 February 1845, to which the railway agreed, and the shareholders sanctioned the action soon afterwards. They engaged a Parliamentary agent to handle the details, who realised that the original Act of Parliament, dating from 1790, expressly prohibited the Trustees from leasing the canal. By September, the two sides had agreed that each of them would seek to obtain powers to overturn the clause. The railway company would pay £1,070 per year for the first 21 years, and £850 per year for the second 21 years. The Trustees sought an Act of Parliament to authorise this, which contained a clause requiring the railway company to maintain the navigation. The House of Lords were not convinced that the clause was strong enough, and amended it to ensure that the railway had to maintain it "in as good a state and condition as the same shall be at the time of passing of the Act." With this amendment in place, the Act was passed on 26 June 1846.
Meanwhile, the railway company was obtaining its own Act, which had initially included a similar clause about maintenance, but this had been dropped by the time the Act was passed. The Railway Commissioners voiced their concern that the railway had somehow managed to gain control over a navigation without any of the details being included in their own Act. They raised the issue in their report to Parliament in 1847.
The line opened in 1846, and with it came a serious decline in traffic on the navigation. The condition of the waterway declined, and the Railway Commissioners asked the Great Eastern Railway who had taken over the Eastern Union Railway, to repair the defective sections in 1869. When the 42-year period of the lease was close to ending, the two sides met, and the railway declined to extend the lease. The navigation was by this time in a poor condition, with little traffic, but because of the clause in the 1846 Act, the railway company offered the Trustees £2,000 in lieu of repairs. This was agreed on 5 January 1888, and the money was paid on 23 March.