What is the locomotive class with the most stroke whose operator is Lancashire, Derbyshire and East Coast Railway?
select ?ent where { ?ent wdt:P31 wd:Q19832486 . ?ent wdt:P2557 ?obj . ?ent wdt:P137 wd:Q6482976 } ORDER BY DESC(?obj)LIMIT 5 
locomotive class: Q19832486 lancashire, derbyshire and east coast railway: Q6482976