TfL want to increase the frequency on the East London Line from 16tph to 20tph, and apparently the demand is in the historic core from Whitechapel to Surrey Quays. It occurred to me that if the Gatwick Express to Victoria was scrapped, and instead 4tph from Gatwick (or Brighton) ran to New Cross Gate, called at every station to Whitechapel, crossed over the GEML and then used a new ramp down to the north side of the GEML to serve the low-numbered platforms at Liverpool Street before reversing to Stansted to replace the Stansted Express, this would give a crucial new link from Liverpool Street to Gatwick, as well as being occasionally useful for journeys like Tottenham Hale to Gatwick or New Cross Gate to Stansted. The new curve would go through the Bishopsgate Goods Yard, which I think is listed, but I think this would be allowed, and would probably be the cheapest useful new rail link possible anywhere in London, if not Britain. The trains would probably be several carriages too long for the ELL stations, but I don't see that as a show stopper.
(Obviously I am aware that the ELL used to connect to the south side of the GEML long before the current bridge over the GEML was constructed.)
(Obviously I am aware that the ELL used to connect to the south side of the GEML long before the current bridge over the GEML was constructed.)