In some events (including top-level marathons like London or Berlin) pacing is legal as long as the pacer is themselves entered in the race. Historically record

In some events (including top-level marathons like London or Berlin) pacing is legal as long as the pacer is themselves entered in the race. Historically records wouldn't count if the pacer didn't finish, but I don't think that's still the case. For instance, in Roger Bannister's record-breaking four-minute mile run, Chris Brasher and Christopher Chataway acted as pacers. According to a prearranged plan, Brasher led the first two laps, then dropped back (and finished last). Chataway then led, until Bannister kicked with just over half a lap to go.