Lewisham has been a bit of a nightmare ever since they started trying to make it accessible, along with the addition of the DLR platforms. It’s come a long way since the only entrance was at the London end of platforms 2 and 3 and access to platforms 1 and 4 was via a subway at the same point. Platforms 1, 3 and 4 now have new entrances part way along the platform with a series of lifts offering step-free access. However, the position of these lifts and stairs mean that a lot of the walkways have to be outside the paid area of the station. So in addition to the out of station interchange (OSI) between National Rail and the DLR (20 minutes) there is also a shorter one between gatelines within the National Rail station (15 minutes). Both seem excessive, but if you have to wait for multiple lifts to arrive you may well need the extra time.
All this seems straightforward until you consider wanting to end a journey there and start a new one a few minutes later. Not that common, but one scenario might be estranged parents handing a kid from one to the other. The Oyster processing system seems to know which gates you have used for out and in and won’t apply the OSI if you’ve used the same set of gates. However, the back office contactless system doesn’t appear to get the individual gate info so it will join the journeys together regardless. Fortunately contactless will break an OSI if you end up doing a here to here journey (eg Lee to Lewisham to Lee in one go). The same journey(s) using Oyster might end up with one or more incomplete journey charges unless you are careful to use the same gates.
However, the reason I wanted to do this was to save a little money. The National Rail operators will do anything they can to ensure that contactless caps at the same rate as Oyster. I recently travelled from Crayford into London off-peak and then made several journeys within zones 1-2. Suddenly I noticed that I’d capped at £10.45 which is a pretty unusual figure for adult fares and caps which are all multiples of 10p. Clearly the cap was the zone 1-2 one at £7.40 which meant that they had charged me £3.05 for Crayford (6) to zone 3. This is cheeky because the off-peak single fare for Crayford to Lewisham (2/3) is only £3.00. So on the way home I decided to be crafty and get off at Lewisham, touch out and back in, then continue to Crayford. The first Lewisham train wasn’t a Sidcup line one so I didn’t lose any time. Despite using the same gate I was still charged a £3.05 extension fare because contactless joined the two journeys together.
Will contactless always charge you the same fares as Oyster – no. Passenger A has a weekly zone 1-2 travelcard on their Oyster card and makes a trip out to Crayford one evening. They will be charged £3.00 singles for zone 3-6. Passenger B uses a contactless card and caps for the week at the same price as the zone 1-2 travelcard. Their additional trip will be charged £3.05 singles. All so that £7.40 + £3.05 + £3.05 = the zones 1-6 cap of £13.50.