Under what circumstances the half race passing time in a marathon qualifies for a half marathon competition?

Question

Few months ago, a track and field runner Carles Castillejo was involved in something quite interesting: he wanted to qualify to the IAAF World Half Marathon Championship 2018 in Valencia, Spain, to be held in March 24.

He tried to get the minim time in Barcelona on February 11 but he failed due to a flu: he ran in 1h 04:57, while he needed 1h 04:30.

Since he felt he was capable to get the time, he managed to do so in a particular way: he ran the marathon of Seville on February 25, only that running the first half marathon in a fast pace, which would count as official time. As indicated in Carles Castillejo, a por todas en el Zurich Maratón Sevilla _{Spanish, translation mine}:

He will be the pacemaker up to the km 15 of the race. Then, he will try to make the half marathon in 1h 04 to get the classification [to the World Half Marathon Championship]. To make a valid time he must finish the race.

As explained by the IAAF on Seville's marathon report, this is what happened:

The men’s race opened at a frantic pace as the two kilometre point was reached in 5:55, ten seconds ahead of schedule. Once the organisers managed to slow the pacesetters, it was the first pacer, Spain’s Carlos Castillejo, who led the main group through 10 kilometres in 29:58. All the main favourites were tucked in behind him except for Spain’s Jesús España who opted to travel in a second group, well behind.

Castillejo, 39, led the lead group through the halfway point in 1:03:30

After that, he just managed to arrive to the end with an approximate time of 2h 23, which just did not matter.

So my question is: under which circumstances is this possible? What if the marathon was just going down for 21 km and then going back up?

Foot note: he finally could not run with his national team, due to some law interpretation problems. However, he ran the mass race just behind the professional one and managed to overtake most of the runners, as described by the IAAF in Castillejo comes out from the crowd.

Answer 1

This is a tricky question, but it is not at all uncommon for split times ("intermediate" or "en route" timings) to be submitted as record performances, particularly in longer road races like 30km or 35km which run as often as longer distances like the marathon. IAAF Competition Rules 2018-2019, Rule 260 states:

World Records in Road Running Events set at intermediate distances within a race must comply with the conditions set under Rule 260. The intermediate distances must have been measured, recorded and subsequently marked as part of the course measurement and must have been verified in accordance with Rule 260.21(e). (emphasis added)

Put more simply, this says that as long as the intermediate distance meets the measurement and verification standards for a record, it's eligible for the record. (So your example of a marathon which is downhill for the first half and uphill for the second half is important - a halfway split from the Boston Marathon, for example, would not be record-eligible.)

Because the measurement and timing standards are more exacting than road races normally apply for intermediate times, an athlete hoping to set a record (or record a qualifying mark) at an intermediate split would as a matter of course notify the race management in advance; some races, like the Berlin Marathon, anticipate this and arrange measurement and timing on their own initiative.

The standards for qualifying times are likely to be less stringent, and may even vary from country to country (if the national federation has stricter standards than the IAAF's qualifying marks) but if it's possible for records it should certainly be possible for qualifying marks where the stakes are much lower. The need to finish the race in order to have the "en route" time count would certainly make this route more difficult than just running a race of the appropriate distance (if one is available).